ATC filing in USA

[dc9-32]

How do we file a FPL in USA when the callsign begins with a number ?

According to the FAA:

If the AID starts with a number, review format requirements & resubmit.

[dallas]

Have you tried calling flight services and asking?

I'm sure you have it, but: [phone]

[dc9-32]

Yes and they are stumped too but the guy is going to try to figure it out.

[dallas]

...and they must have had a 9H- at some point...

[dc9-32]

FAA filed it manually with an X in front of the actual call-sign.