The real question would be how long it would take to build one, and at what cost. In the case of the P‑8A Poseidon, it took the U.S. 30 years to create it by modifying an existing aircraft to meet the requirements of military forces.
I believe it cost in excess of $8 billion to actually make those modifications. The point I would like to emphasize here is that the modifications we're talking about to take a civilian aircraft and modify it into something military are very complicated and very expensive. These are not easy modifications.
It's not that they cannot be done—