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Gliders have no engines, so they are typically taken to height by a powered aircraft. When they are released, they trade distance for height. In flight they can also use updrafts to gain height, but must avoid downdrafts.
Some gliders can take off from a cliff, but cliffs aren't available near every airport location. I suppose that one could lift a glider with a balloon, but that would make the whole process much slower, and would probably be no faster than ground travel (e.g. by train).
Lastly, gliders are typically light-weight, and cannot carry more than one or two people.
I suspect that the economics would make using gliders impractical for travel purposes. Ground travel by train is likely to be much more efficient.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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I know the Germans developed a giant glider plane in WW2 that could carry a lot of soldiers or even a tank, but at the time it was not very practical and they did not use it as far as I know.
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And it had to be lofted by a powered plane, so I don't see where the great savings will be coming from.
Gliders have their place, but passenger aviation isn't one of them.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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I have often seen gliders being launched by using winches, seems more eco-friendly than using towing planes to me.
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And how large were those winch-launched gliders? From a cursory search of the Internet, we are talking about a few hundred kg.
As Griff said, the Allies used gliders in WWII. These were towed by aircraft and released from the air. However, 28 people or 7 tons of cargo are a small fraction of the cargo capacity of a 707, to say nothing of more modern aircraft.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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We need bigger rubber bands.
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The advantage would have been tactical, given that the glider would have been silent. Aircraft engines in that era were very, very loud.
Software Zen: delete this;
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Yes, but the OP was discussing civilian gliders, in which the main driver would be commercial. Yes, they are quieter, yes, they are more fuel-efficient, but the carrying capacity is very low compared to even a small commercial aircraft. This means that the number of takeoffs and landings would have to be much higher than the present number. Most commercial airports don't have the spare capacity for this.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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I can't help but remember how I enjoyed the silence when all aircraft were grounded during the pandemic.
Aircraft engines are still very loud.
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Daniel Pfeffer wrote: so I don't see where the great savings will be coming from.
A possibility back then would be to get close without noise.
M.D.V. 
If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?
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The British had the Horsa (capacity 28 troops) and the Hamilcar (load capacity 7 tons) which were used quite often in WWII - they built 3,600 of the Horsa and used over 2,500 in a single operation (Operation Market Garden - Wikipedia[^])
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
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AntiTwitter: @DalekDave is now a follower!
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Yes, but they were towed by powered aircraft. They certainly could not be launched with a winch or from the top of a cliff.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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The allied used gliders in Operation Market Garden (known from the movie - and expression - "A bridge Too Far"). But they where dragged to the destination by powered aircraft - C47 and various bombers. Only the actual landing was completely unpowered. Worked fine to add capacity and capabilities to the powered aircrafts, but I don't think they had any noticable environmental benefits, nor do I I think they would have gone that route if starting from scratch without already having the odd thousand powered aircrafts available.
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Indeed, I doubt there were any thoughts about "environmental benefits" in those days. The main advantage of using gliders was the tactical advantage of surprising the enemy.
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Googling suggests that they considered the primary advantage of the Horsa was that it could put the troops down as one group. Parachutes meant they would be spread out (significantly.)
I suspect, although I did not read that, that is was thus considered disposable - a one use shot.
Also, my supposition as well, that this worked because it would have a much lower air speed on landing (and perhaps cost) so more likely that a short landing could be made.
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Daniel Pfeffer wrote: they trade distance for height.
Just a pedantic correction: they trade height for distance and the "exchange rate" is called glide ratio[^].
Mircea
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Mircea Neacsu wrote: they trade height for distance
You're correct. I reversed the order. 
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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Greetings and Kind Regards
It occurs to me perhaps customer confidence may be an obstacle to overcome. I am not knowledgeable in such matters but it seems reasonable to me to assume a glider of carrying capacity equal to an airliner would be a technical challenge. Certainly worthy of further study. Permit me to say my own pet idea re/ Green Aviation is dirigibles. Unfortunately I can not imagine the aviation public would tolerate the lengthy flight across great distances. Perhaps it is of practical use only for freight.
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Several companies are actively creating large dirigibles for various business reasons.
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I think Dan hit all key notes as to glider economics. Just not there.
Maybe some advanced battery technology in future might tame electric power for powered flight.
Glider technology may go hand in hand.
"A little time, a little trouble, your better day"
Badfinger
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Who knows, maybe some kind of hybrid technology with batteries that are not too heavy and only used for take-off or emergency situations ...
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RickZeeland wrote: only used for take-off or emergency situations ...
If the batteries are only used in these situations, they will not be installed at all.
Takeoff power can be provided by an external source (winch, tow aircraft, etc.), so the use case simply isn't there.
In emergency situations, the pilot may need large amounts of power for a short time. Batteries that can do this are very heavy, and would be mostly parasitic weight. Technical improvements would better be invested in improving safety. There is a saying "A clever man can get out of situations that a wise man won't get into". That should apply to safety considerations.
Another reason for not having large batteries on a glider is that gliders are relatively flimsy. In an emergency, the kind of stress that a commercial aircraft can handle might snap the wings of a glider, causing the very accident that one wishes to avoid.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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All true.
Fuel tanks get lighter with use. Not so with batteries.
Power could be solar but that's been done and it's very tricky in cloudy weather.
Interesting challenge, though.
"A little time, a little trouble, your better day"
Badfinger
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Well there are plenty of examples of gliders being launched by (electrically-powered) winch, so that could be an environmentally-friendly possibility. However gliders are even more weight-sensitive that powered aircraft, so I'm not sure people would be happy without their duty-free chocolate sales etc.
However... almost 50 years ago I worked doing research into energy savings in railway operation through coasting (i.e. power-off) when trains were running ahead of schedule, and energy savings were significant. I'm also aware of aircraft incidents where for various reasons all engine power has failed, and airliners have glided 50 miles or more[^] to their destination. Of course, as noted elsewhere, you trade height for distance and, without engines running, you severely limit your options in the case of emergency. But there might be a case, if it's technically possible to virtually guarantee an engine restart in-flight (given sufficient fuel of course), to argue that maybe aircraft could delay their powered descent and simply cut their engines at 30,000 feet and glide the final 50 miles - reducing pollution, fuel use, and noise - whilst retaining the ability to power-up in case of adverse winds, go-arounds and diversions. Aircraft engines not only provide propulsion, but also power for auxiliary services like air-con, hydraulics, comms etc so the APU (Auxiliary power unit) would need to keep running throughout.
It would certainly make for an interesting study...
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Greetings and Kind Regards
It is not re/ gliders but rather another somewhat surprising aviation technology so perhaps the YouTube video link below may be of some interest to your kind self.
Could This Change Air Travel Forever? - YouTube[^]
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