Lots of other steps...
Including some rather large legal hurdles, in this case.
https://en.wikipedia.org/wiki/Antideficiency_Act
Note that this is not the familiar, legally codified Multi-Year Procurement because they are doing it long before the contractor has fulfilled EMD obligations (that is, successful IOT&E of a contract-compliant aircraft). There have been a few "block buys" that were not MYPs (the Virginia SSNs, for instance) but those were not joint-service, let alone multi-national, and they have been strictly case-by-case in Congress.