A 26-17 reverse in Cardiff followed on from the Reds’ 16-14 loss to the Royal Navy and the result saw the airmen claim their first silverware in the competition for 19 years.
An early try from wing Spr Will Sevodi (RE) gave the soldiers the perfect start in Wales, only for their rivals to strike back and level the contest at the break.
The champions-elect moved through the gears in the second half with AS1 Kieran Jenkins taking centre stage.
The fly half slotted a brace of penalties before crossing for a superb individual try, and a second score then saw them take command of the tie.
The army hit back with two efforts late on, but the RAF held firm to secure the win.
Elsewhere, the army men’s sevens team will head to Fiji later this month to compete at the Coral Coast Sevens tournament.
A 14-man squad has been named for the competition, which will be staged at Sigatoka’s Lawaqa Park from January 15 to 17.
