Ranksof squadron boses in the RAF

[Max Contingency]

I assume you are talking about flying squadrons (we do have many others!)

There are some sqns (rotary/trg etc) where the OC is a sqn ldr. Sometimes a flt lt may stand in for a lengthy period of time.

Most sqns have a wg cdr OC. Sometimes the OC is promoted gp capt while still in post and holds that rank until starting the next tour.

So in answer to your question flt lt to gp capt.