Rich Lovelace writes:

The last airline out of UK to carry gliders is no longer going to!

http://www2.virgin-atlantic.com/us/en/travel-information/baggage/sports-equipment.html

For bookings made on/after 01 June 2016 standard dimensions of
190cm x 75cm x 65cm (75" x 30" x 26") and 23kg will apply regardless of the
equipment type. In addition, we can no longer carry the following:

- Canoes and kayaks

- Hang gliders

- Windsurfing equipment

Jamie Shelden writes:

You're all forgetting about United. They have flights from
Manchester and London and they happily take gliders for $200. Their sports
baggage policy is even written in such a way that you can take all of your hang
gliding equipment (harness, spare parts, glider, etc.) in up to 4 different
bags! The only potential problem is they won't accept a glider on a 737 or
A320/A319. So, you have to make sure your connection isn't on one of those
aircraft. From Manchester, that means that you would be routed through
Frankfurt, which is a little bit of a pain, but still totally doable.