When pilots check in with a different controller, how to reference flight level?

Question

When pilots check in with a different controller after they are handed off, how do they report their current altitude in flight levels if they are in level flight or a climb / descent? I feel like saying "level flight level" could be misunderstood.

Can pilots omit the "flight level" phraseology in the examples below?

"(ATC Facility) Baron x-ray five x-ray sierra level flight level two-five-zero... " (level flight @ FL250)

"(ATC Facility) Baron x-ray five x-ray sierra flight level two-five-zero climbing flight level three-two-zero..."

"(ATC Facility) Baron x-ray five x-ray sierra flight level two-five-zero descending flight level two-zero-zero..."

Answer 1

The word 'maintaining' is used, not 'level'. Using your example it would be:

• (ATC Facility) Baron X5XS level maintaining FL 250.

The pilot can say maintaining if they're expecting higher/lower, otherwise omit maintaining altogether:

• (ATC Facility) Baron X5XS FL 250.

If climbing/descending:

• (ATC Facility) Baron X5XS climbing/descending FL 100.

On the first contact with a radar service, for example going from tower to departure, the SID and passing altitude are also mentioned:

• (ATC Facility) Baron X5XS on the STACK 1C passing 2300 for FL 60.

In a busy environment you may be asked to 'report call sign only', in this case:

• (ATC Facility) Baron X5XS

Local guidelines should also be used if different. I couldn't find examples in ICAO Annex 10 and Doc 4444, but clear examples are in the UK's Radiotelephony Manual (click image below to view).

Answer 2

You didn't say which country you're interested in, but in the US the standard phraseology is indeed to use "level" twice. This is from the AIM 5-3-1:

When operating in a radar environment: On initial contact, the pilot should inform the controller of the aircraft’s assigned altitude preceded by the words “level,” or “climbing to,” or “descending to,” as appropriate; and the aircraft’s present vacating altitude, if applicable

EXAMPLE −
1. (Name) CENTER, (aircraft identification), LEVEL (altitude or flight level).

Per 4-2-9, the correct way to state a flight level is:

At and above 18,000 feet MSL (FL 180), state the words “flight level” followed by the separate digits of the flight level.

So put all that together and you get something like this:

Indianapolis Center, N12345 level flight level 210

Practically, I hear a lot of pilots omit the words "flight level", perhaps because they seem superfluous:

Indianapolis Center, N12345 level at 210

As for misunderstanding, personally I think that's unlikely even if you use the word "level" twice. A flight level is stated as three digits ("two one zero") whereas an altitude always includes the units, i.e. thousands and hundreds ("five thousand five hundred").