Would this "being paid while flying" scenario be considered "flying for compensation"? The difference between a private and commercial pilot's license hinges on this critical ability to expressly receive pay for flying; a PPL is allowed to fly "in furtherance of a business" but cannot be paid to fly a plane, while a CPL can. That brings up an important question; in today's corporate world, there often isn't a strict "hours for pay" exchange; you get a salary, for which you perform the duties of the job (which do not necessarily mean being there 8 hours a day). So,  what's the difference between being paid while flying in furtherance of a business, and being paid for flying?

A simple example (I hope): I'm a salary man, and my workplace happens to abut a public air park in Dallas. A coworker of mine needs to get to Waco to have a short face-to-face meeting with a client (teleconferencing won't do), and my boss knows I'm a PPL and own a fairly speedy Cherokee 235 (cruising speed 135 mph). The forecast for tomorrow is perfect flying weather, so he proposes this deal; I commute to work in my plane tomorrow instead of driving. After morning coffee and e-mails, my coworker and I will head over to the air park and fly out from there to Waco in my plane and be picked up by the client. We'll have the meeting, be driven back to the airfield, and I'll fly us back to Dallas so he can drive home.

For this, I'll get paid for the workday as I normally would, no vacation or other leave time required to be used. My boss also suggests that I can expense my fuel costs and any landing fees, like I would be able to do with my gas and parking fees if I drove. My boss gets two people face-to-face with the client faster than if we drove, with less time off our normal duties than if we flew on a regional jet (and much cheaper), and I get paid to fly my plane without being explicitly hired to do so.

The questions:


Can I accept the deal at all, or will the fact that I'm technically being paid while flying be considered the same as being paid for flying even though no additional money specifically for my yoke time is changing hands?
What portion of my out-of-pocket costs can legally be expensed?


All my fuel and landing fees incurred between taking off from and landing back at my home field (which I otherwise would not have incurred)?
100% of costs from when I take off at the air park near work to when I return there (the portion of the flight in furtherance of the business)?
50% of "non-commuter" flight costs (gas to and from Waco and the landing fee there, but not the fees at the air park or gas to and from my home field)?
No expenses allowed (because that would be "compensation for flying")?

Would any of this change if I were an hourly employee doing this "on the clock" as opposed to being salaried?
Would any of the above answers change if my boss wanted me to rent a speedier plane (that I was rated for of course)? Would I be able to expense some or all of the rental?
I'll try not to make this an off-topic "legal advice" question: if I refused the deal because I thought it would violate the restrictions of my PPL on flying for pay, and I was summarily fired, should I be talking to a lawyer about a wrongful termination suit?
The short answer is that you'd need a commercial certificate, and potentially a commercial operator's license, to do what you're describing. Standard disclaimer: IANAL, and if you wanted to do anything like this, you really should find an aviation lawyer and get answers from them in writing!

The rules that cover this are contained in FAR 61.113, quoted in relevant part:


  §61.113   Private pilot privileges and limitations: Pilot in command.
  
  (a) Except as provided in paragraphs (b) through (h) of this section, no person who holds a private pilot certificate may act as pilot in command of an aircraft that is carrying passengers or property for compensation or hire; nor may that person, for compensation or hire, act as pilot in command of an aircraft.
  
  (b) A private pilot may, for compensation or hire, act as pilot in command of an aircraft in connection with any business or employment if:
  
  
    (1) The flight is only incidental to that business or employment; and
    
    (2) The aircraft does not carry passengers or property for compensation or hire.
  
  
  (c) A private pilot may not pay less than the pro rata share of the operating expenses of a flight with passengers, provided the expenses involve only fuel, oil, airport expenditures, or rental fees. 


To point 1, the answer is no. You're being compensated for your time, which is spent flying. If you were alone, 61.113(b) would allow you to be compensated - but that only applies if the aircraft does not carry passengers. Since the 61.113(b) exclusion doesn't apply, you're stuck with 61.113(a)'s prohibition of flying for compensation or hire.

You make an interesting point at the beginning about salary covering strange hours. If you really were paid just for your productivity, and you had an arrangement where you could just go take a couple of hours off in the middle of the day to go flying (or any other personal activity) without burning leave or affecting your pay, you could claim that you weren't being compensated for your time. I might write to the local FSDO for clarity on that before actually doing it, though.

If you were an hourly worker (#3) and were not paid for the time you were flying, that would eliminate some of the compensation. Note, however, that the FAA constructs "compensation" very broadly, to include good-will from others. If you made this flight in order to make your boss happy, you're being compensated! The source of the incentive to fly would be important: if you and a co-worker had to get to a destination, and you suggested, "Let's fly there!", you're under much better grounds than if your boss told you to.

The second point would depend on your normal work situation. Let's look at two portions of the flight:


The portion from home to work, and from work back home: In this case, you could be compensated for the flight under 61.113(b) - both in salary and costs, as long as your employer has a policy of reimbursing staff for their commuting costs.
The "non-commuter" costs: You could ask for 50% of the costs of the flight under 61.113(c) (see Mangiamele interpretation) - but from your co-worker, not your employer. Where they get that money is up to them. One important point: 61.113(c) requires "bona fide common purpose" -- you and your co-worker must each have a reason, beyond the flight itself, for going to the destination airport. If you weren't required to meet the client (or do something else that requires you to physically be in Waco at that time), you could not even share the costs of flight. Note that you can't be paid or reimbursed for your 50% — you have to eat that cost yourself.


To #4, the owner of the plane doesn't matter that much here, for a private pilot. The question of who provides the plane becomes very important in common carriage, but that's a different question.

To your last point, I'm not a lawyer - but I imagine that being fired for refusing to take an illegal action would be wrongful termination.

Further Reading:

An FAA Article on cost sharing

Mangiamele Interpretation: a letter from the FAA Office of Legal Counsel discussing this topic