It all depends on your money and the rate of depreciation. Higher depreciating aircraft (Canadair Cl-44, Sud Caravelle, Boeing 747-8I) are much more profitable to lease for the first few years, as you end up paying less on leases than you would maintaining such a high depreciating aircraft. As these aircraft hit 7 yrs of service, begin to buy them. As half your lease goes into buying an aircraft, it comes up as free (or very little). For aircraft with low depreciation (Canadair Cl-215, Embraer Ejets, 737NG and, in fact, most modern aircraft) it makes financial sense to buy these, paying $100k a month on depreciation instead of 600k on a lease. For these aircraft, you'll get a much higher resale value (Cl-215s can be bought for $2.3M, sold after about 20 years for $1.9M).