Are you sure they are "Air Numbers" and not WBCCI numbers?
Most likely, they are WBCCI numbers and they are membership numbers that go with the people as members rather than the trailer. So that would mean that your trailer was previously owned by two different members. People usually put the new numbers over the old ones because traditionally they go over the window front and back. In some cases, a new WBCCI member can obtain the old numbers if
the old numbers are no longer used by the previous member for at least two years. If they are still in use, a similar number can be requested to cover up the old numbers substuting 3's for 8's, etc.
As far as finding out who the numbers were originally assigned to goes, there are several people here online that have old WBCCI membership directories and can look them up for you. Check out this thread
to see who does this sort of thing.
AirForums numbers are a relatively new thing - it is highly unlikely that your trailer would have already had two previous owners that would have displayed their Air numbers.