That's not a license!

[Circuit Basher]

Bejasus, you get all sorts of discussions on Private Flying, don't you??!!

Just checked the copy of Concise Oxford Dictionary (5th Edition, from around 1968) that I have at work and -ence is given as the primary spelling for the noun (eg the Private Pilots Licence) with -ense given as an alternate spelling. However, -ense is given as the primary spelling for the verb (eg the CAA licenses pilots) with -ence given as an alternate spelling.

Traditionally, the -ense ending is regarded as being the US version, but my dictionary (old as it may be) does not uniquely accredit that spelling to the US alone. I'm personally in the -ence camp, myself!!