I've done a little research and the simplest explanation I can come up with is outlined in a couple of Chief Counsel Opinions from 2007 and 2005 (links below).

http://www.faa.gov/about/office_org/...07/schwarz.pdf

http://www.faa.gov/about/office_org/...ill135267f.DOC

They both state that in order for time to be counted as "rest," it has to have three criteria. Rest must be 1) continuous, 2) determined prospectively, (i.e. known in advance) and 3) free from all restraint by the certificate holder, including freedom from present responsibility from work should the occasion arise. Nowhere does it say that "on call" time is considered duty time, but it's also not considered rest time. The book "Everything Explained For The Professional Pilot" by Richie Lengel seems to agree with this.

One of the most interesting things I came across is that if you look at the rest time requirements laid out for flight attendants in 135.273 (by flipping the page after looking at the pilot duty time regs) you'll see that it begins with definitions for calendar day, duty period, and rest period. If those same definitions were copied word for word into the beginning of 135.267 (the flight crew rest time requirements) there wouldn't be any question about it.

At my company we're almost definitely in violation because we're on call 24/7 and are paid on salary. Therefore we are more or less required to take any trips that come up. (Obviously we don't do anything crazy or unsafe, but pop up trips are fairly common.)

I still have a few questions that I haven't been able to figure out:

1. Does anyone know of a company (or pilot for that matter) that's ever been violated because of this? I'm guessing you can't look this up on the FAA website, but obviously someone got in trouble back in 1999 to prompt that appeal to the first circuit court.

2. How would a company successfully operate a non-scheduled operation without being in violation of the law? As far as I can tell, you can either operate on a ten hour callout so you can get your rest time in, or you can count your on call time as duty time and only be on call for 14 hours at a time. Of course when the average trip (in my case anyway) lasts about 12 hours you can only really be useful for the first two of your 14 hours. Any ideas? By the way, apparently the NATA wants to change the rules. I found a proposal for it here:

http://www.nata.aero/filedownload?da..._ID&rowId=3590

That's all I got.