Confusion on the Whitlow letter
 

No, you need CR1 (10 hours), not CR2 (11 hours), because you were scheduled to operate less than 8 hours in a 24 hour period in this case. While I don't know your schedule for day 2 (or day 0, if this is in the middle of a trip), I'm assuming that since you say you were scheduled for NR1 originally, that was legal, so that would trigger CR1 (10 hours).

Whitlow triggers comp rest over 15 hours of duty day (because @ 15:01 of duty you now have less than 9 hours of lookback rest in the preceding 24 hours, you therefore are automatically on reduced rest and need compensatory rest when you duty off).

The amount of rest required (reduced, normal, or compensatory) is totally unrelated to the length of your duty day - it is based on your scheduled flight time - not actual flight time.

Yes, this means that you can fly 9+ hours in a duty period, trigger the whitlow letter with an over 15 hour duty day, and still only require compensatory rest of 10 hours when you duty off. Because though you flew 9+ hours, you were scheduled to fly less than 8 hours, which is what determines the length of your rest period (<8 hours flying = 10 hours normal rest). Whitlow then puts you into compensatory rest based on your original required normal rest (you were required 9 hours, so compensatory is 10 hours).

Not so fast. Whitlow does not define when a duty period ends (block-in or at the end of postflight). There is more to this 'caveat'. As you say, Whitlow only has to do with duty time. A scheduled postflight is duty time. The caveat is '121 duty time'. Some shady operations (ie, regionals) say:
'FAR 121 does not require a postflight, only a preflight. The company requires a postflight. Therefore, your postflight is FAR 91 duty, not 121 duty. As such, your FAR 121 duty day ends at block in, not duty off, you are under 15 hours or FAR 121 duty, and you don't need compensatory rest.
While this is playing loose and fast with the intent of the Whitlow letter, it is legal. If your company plays this game, then essentially you need a '15 hour and 15 minute duty day' (including your 15 minute FAR 91 post flight) to trigger Whitlow rest.

It is important to know what is going on here (FAR 91 post flight). Don't just assume your Whitlow duty day ends @ block-in. That is NOT the rule.

15:46 minutes of scheduled FAR 121 duty, with a 15 minute postflight.

• FAR Part 121 postflight = no, as you leave the gate you will have you have 7:59 of lookback rest, you can't take the flight.
• FAR Part 91 postflight = yes, you will have 18:14 of lookback rest. As you take the runway, check to make sure you are still scheduled to land allowing you to have 8:00 or more of lookback rest. Ie, you can take a 14 minute delay on taxi-out and still be legal.

Thats what I thought and that was the position I was going with, but I had another guy try to say that the Whitlow letter says "look back" so that meant also include actual block. I didn't think that was right and went into the books and they were slightly grey in that area wording wise so I figured I'd come on here and see if any one else had more defined wording.

This "postflight" term is way confusing as to what the meaning is. Duty time is report to release for a line holder and beginning of phone availability to release (if assigned a trip) for reserve. You are making it sound like a literal post flight walk around in your description and that is not the intent. You get a "debrief" time after block-in to allow for parking, termination checklists and removal of your items from the airplane while passengers deplane. Most companies I know of have 15 minutes of "debrief" time because you are certainly not OFF duty the moment you block in unless you are sitting on the plane as a deadheader.

So, the pilot would not be legal to go with a 0600 phone availability start and 2146 arrival + 15 minute debrief = 2201. On duty more than 16 hours (16:01) which equates to not being able to look back and find 8 hours of rest (7:59).

Now remember that is just for assignments. The devil is in the details of the paperwork, flight time, and the calculations of crew critical off time (CCO). Once you are at the runway, duty start + flight plan time + taxi in + debrief all combined have to keep you under 16 hours.

Also, Whitlow does not apply to international flying, though most regionals and some other companies agree to treat Canada and Mexico as domestic operations for ease of work rules and duty times (which is actually a plus because Whitlow is more restrictive).