one engine inoperative (OEI)

all for one and one for all / one for all and all for one

engine capacity / engine power, engine output

one-way UAV / one-way attack UAV (OWA UAV)

be on one's high horse / get on one's high horse

one-shaft gas turbine engine

reaction engine / motor (jet engine)

rotary engine (Wankel engine)

engine ground run / engine test

engine oil reservoir / engine oil tank

airbreathing jet engine / ducted jet engine

commission, to resign one’s commission

complete one's tour

force one's way

hoist / strike one's flag

inch one's way forward

one day’s supply

one-man turret

one-piece

one-piece base

one-shot weapon

one-time report (on status of equipment etc.)

one-time report

one-up

overstay one's leave

prescribed range (running-time on one fuelling)

push one's way

reverse one's field

strike one's flag

tighten one's hold

wet one's stripes

win one's epaulets

celebrate (one's) stripes