This question was inspired by this other question. If a private pilot was to pay the pro-rata share of a flight for some skydiving friends, could they take those friends up and let them jump out?
If so, what counts as "pro rata share"? Is it expenses for the whole flight from takeoff to landing, or does the pilot assume 100% of the cost after the point where the skydivers leave the plane?
This is not so difficult. Many people like to refer to the regs without actually looking at the regs. This is all taken from §61.113.
Pro rata share is not the same as getting compensated.
(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.
In this scenario, the pilot isn’t holding out as a commercial operator; these are his friends.
According to any online legal dictionary, the pro rata share is defined as the total cost divided by the number of shares. In other words, the total cost of fuel, oil, airport costs, and rental fees split evenly between everyone in the plane, including the pilot. As long as it is split evenly, it’s not compensation or hire, it’s cost-sharing.
All that said, NEVER do anything because some guy on stack exchange told you that it was ok. Check the regs for yourself and contact your local FSDO for clarification.
If the pilot and skydivers maintain true integrity and aren't actually exchanging money or favors, then yes, it is legal.
Let's look at a couple of possible scenarios.
Scenario A: Three private pilots who have skydiving certification take turns flying the plane for each other while two of them dive. They go up acting as the pilot an equal number of times, and they all split the cost of the aircraft 3-ways. None of them were compensated or hired for their turn flying, and they all paid a pro-rata share.
This is clearly legal, and this scenario above sounds plausible and makes sense to an outside observer.
Scenario B: a pilot agrees to spend hundreds of dollars to take two other people skydiving for no compensation and even agrees to split the cost of renting the plane 3-ways. (*How generous of him...)
If this were actually what was happening, this is perfectly legal. However, it is suspicious; I think that if this got the attention of the FAA, they might start wondering how the pilot is really being compensated.
Is one of the skydivers mowing the pilot's lawn for free as "a favor"? Did one of them let you borrow his backhoe a couple of times to do some landscaping? Are they watching your kids while you're at work?
The FAA ultimately decides what compensation is, and it doesn't necessarily mean cash, so be careful with this.
A private pilot may possibly get away with dropping skydivers when there's no question of compensation whatsoever, but the FAA may see that differently as they consider skydiving flights as commercial operations.
Whenever there is compensation for a flight (regardless of whether the pilot is compensated), that flight is considered a "commercial" operation. Nearly all jump flights involve compensation and, by FAA standards, skydiving flights are commercial operations. [...] The FAA requires pilots to hold at least a current commercial pilot certificate, along with a current second class medical certificate.
There are some matters to consider for the aircraft used for the operations as well.
When an aircraft is used in a commercial operation, the aircraft is subject to a 100-hour inspection, as well as an annual inspection.
And:
Federal regulations (14 CFR Part 119) describe the certification requirements for air carriers and commercial operators, but exempts skydiving flights operating within 25 miles of the departure airport. As a result, skydiving flights are conducted in accordance with 14 CFR Part 91 and 14 CFR Part 105.
