It is not the cost of the round trip flight that matters. It is the cost of that round trip plus the cost of "ownership" of the aircraft and the overheads. I appreciate that in Silver the overheads are likely to be low but they do include all salaries.
Silver has gobbled at least £50 million of shareholders funds in the last year plus any loans. At that burn rate who would lend them more? It is a bit like asking a drain how much money it wants to take from your pocket.