I'd translate 'volar a vela' as 'to soar' - when talking about raptors etc. soaring.

HTH


Sheila


Definicions de soar a la xarxa en Anglès:

rise rapidly; "the dollar soared against the yen"
hang glide: fly by means of a hang glider
fly upwards or high in the sky
go or move upward; "The stock market soared after the cease-fire was announced"
the act of rising upward into the air
sailplane: fly a plane without an engine
wordnet.princeton.edu/perl/webwn


fly upward, as in: We watched the eagle soar into the sky and disappear.
www.business-words.com/dictionary/S.html


ALA - Internet
Soar, Elevarse, remontarse; volar a vela (avia). Soaring flight, Vuelo a vela (avia). Soaring glider, Velero (avia). Soaring in thermal u, currents ...
www.ala.aero/ala2/diccionario/dic_alfa_en.