On Sat, 28 Oct 2006 17:10:46 GMT, wrote:

If you assume that each aircraft went into service the year of its
airworthiness date, you can get the fleet size by year:

Actually, that date (fields 229-236) relates more to the current owner, than the
manufacture date. My airplane, for example, was built in 1982 but the
Certificate Issue Date is when I registered the aircraft in 1996.

Fields 52-55 contain the official "Year Manufactured." Unless the FAA has
revamped its file format, in which case I am going to be well and truly ticked
off (since I have a ton of queries, etc. that would have to be altered to match
while maintaining their compatibility with previous years).

The effect of using the Certificate Issue Date would be to skew the results
towards later years, since a, say 1998 plane sold to someone in 2004 would show
as a 2004 model.

Nice idea, though...re-run your query using the Year Manufactured, and let's
have another look at the data.

Ron Wanttaja