These are either licensed resellers of unused fractionalshares, or they are charter brokers who make arrangements with charter companies who sell blocks of time to them, at a discounted rate.
Last year, the Internal Revenue Service ruled that an unnamed private S corporation could deduct the full cost of owning two fractionalshares in jets, even though those planes were used just 5% of the time for business.
The owners value shares at less than the proportional value of underlying assets on the theory that fractional interests in a portfolio are not worth as much to outsiders.