Flights will consume those miles and fuel much faster than those trees can grow to consume the CO2 from them, so you'd need an exponential number of additional trees planted in anticipation to offset future flights up to a certain point where you run out of reasonable land to grow trees on, or water and nutrients, and then you'd have to expend energy to chop the whole forest down and bury it to still come out ahead. The only way out of the debt spiral is to stop consuming fossil fuels for flight.
