There's a lot of sites out there advertising discounts for groups or help coordinating group travel however I can't find a lot of information on how beneficial this actually is. I'm looking for someone to speak from personal experience what kind of discounts they've received from airlines on various flights, specifically non regional carriers. Also, any tips in booking group travel would be much appreciated.
I don't know if my experience with group ticketing for airplanes is of any use to you, however I'm going to share it.
Every year I take groups of students for language courses abroad and I always face the problem of getting the lowest tariff possible while having everybody on the same plane (they are minors and I can't risk their getting in trouble). What I have found out is that group tariffs are not cheaper than individual ones, on the contrary you normally pay a slightly higher price.
Conversely, you have a few advantages: a. you are required to pay only a limited percentage of the total cost (usually 10 percent) on the spot and the rest can be paid about four weeks before departure; b. you don't need to give the exact names upon booking the flights, so that a person who has agreed to fly may be replaced at no cost if need be; c. the price of the tickets does not change over time.
The trouble with group ticketing is that you need to do it through a travel agency; however, I've never succeeded in buying tickets for more than 4 or 5 individuals over the internet while keeping the same price or even the same flights at times. And another drawback, at least for me, is that internet tickets need to be paid immediately by credit card, and I can't do it for groups using only one card (I would use all my credit and beyond).
One last thing: I've faced this kind of problem while using both regular and discounted airlines, both in Europe and for transatlantic flights.