All that's been paid at present is a deposit to retain build slots. When the time comes to pay up, the company will decide how to finance them. There are various options:
- borrow money from a bank or similar institution
- use any retained profits within the business (unlikely)
- sell the aircraft to a leasing company and lease them back
- ditto with a bank
- set up a company jointly owned with a finance provider which will buy the aircraft and lease them to Monarch
It's unlikely anyone from Monarch will turn up with a wheelbarrowfull of used notes
