Sub-Lieutenant (A)?

[N@alie]

I came across a mention of someone I was looking into in an archive from 1940. I'd previously thought that Sub. Lieut. (A) meant Acting Sub Lieutenant but this clip states:

"Act. Sub.-Lt (A) (initials) (name) to be Sub-Lieutenant (A) (date)" (personal details omitted as possibly still alive).

I dont what the (A) means and wondered if someone could enlighten me please? I've tried the usual search methods but not come up with anything.

Thanks

[Geoffers]

I think it was someone who had qualified with the Fleet Airm Arm

[N@alie]

Thank you Geoffers, much appreciated.