That escalated quickly!
I applaud your good fiscal management. At the same time, I hope you give serious consideration to treating home-brewed automobile maintenance differently than airplane maintenance.
Or is it a recreational airplane and all my questions are missing the mark?
When you compare against super-discount airline airfares for 4 tickets, "our" airplane is slightly cheaper to decide to take it instead of airlines. There are many days when weather-wise it's safe to go by airline jet but unsafe by small airplane. (Of course, there's a massive overhead to that calculus, but day-of-travel is slightly cheaper.) Flight planning and pilot training is time-consuming, so it only makes sense if you already wanted to do that as your hobby. Absent a real desire to do it, it's not worth the time, cost, and risk. Take the airlines or drive.
Do you know much about the environmental/carbon cost comparison between your plane and an airline jet?
I am guessing the smaller plane is better, consumption-wise with gas used per person, than an airline jet?
For the trip to my parents, I have a choice to fly commercial into Myrtle Beach, to fly private into the small airport near their house, or to drive. I'll consider CO2e and a 4-passenger load.
Commercial: 760nm->1300km(693 flight plan plus 10% uplift for ground ops and APU) => 328kg CO2e + 180 miles of airport transport by car => 32 kg CO2e => 360 kg total
Private car: 30mpg, 4 pax, 844 sm => 149 kg CO2e (burning ~28 gallons). (Also is a 14 hour drive, so miserable.)
Our airplane: 616nm => 1200km (including a 5% uplift for climb and ground ops), at 11nmpg, burning about 60 gallons, which matches our actual historical fuel purchases quite closely. Assuming same CO2e/gal as a car => 320 kg CO2e Add 100 miles or so of ground transport and that puts you around 18 kg for the cars and 338 kg total. (Distance is less because we go to an airport that is closer to my home airport and much closer to my parents' house.)
So it looks remarkably close on the airplane side, if the commercial airline figures below are accurate. I'm quite confident the car and our airplane figures are ballpark close enough (absent a math error). That also requires taking a direct flight, which is not always possible (the direct is seasonal). The emissions on connecting flights are much worse than the above with twice as many ground operations. (Jets can burn ~1/3 of their cruise fuel flow while idling on the ground. Pistons are more like 1/6th.)
Refs: http://lipasto.vtt.fi/yksikkopaastot/henkiloliikennee/ilmali... http://lipasto.vtt.fi/yksikkopaastot/henkiloliikennee/tielii...
Even if I could shorten the time-to-full-retirement by a couple years, it wouldn't do me any particular good. I generally like my field and my job. I'm tied to the area (can't freely travel 25+% of the time) by virtue of having kids in 2nd and 4th grade. So, there's no mathematical/financial reason to pursue a more Spartan early-retirement-extreme or MMM-approved spending plan.
With that in mind, I find I'm able to enjoy the luxury expenditures, because they aren't taking us off our plan. We travel for a week each winter to "someplace warm". We travel to visit family quite freely. The kids engage in whatever activities they want to try, without worrying about the costs. We own an airplane. We have cleaners that come by every other week. We buy quality food. We give to charities that are meaningful to us (many with money, some with significant amounts of our time as well).
On the other hand, we cut our own grass, do 95+% of our own car maintenance, almost all of our home maintenance, and cook most of our own meals, because we value the savings and example it sets for our kids (especially around charity and talking through the value of money).