Waiting list for F-16s
The US 'offer' of supplying F-16s to Poland to offset the loss of MiG-29s has been met with scepticism by some experts. Poland operates a fleet of 36 F-16s, which it acquired a decade ago. The US is building new F-16s for Slovakia and Taiwan; as both countries have security concerns, it is unlikely their orders will be transferred to Poland.
Transferring older F-16s from the US Air Force also has complications. US defence website
The Drive noted “No matter where they [used F-16s] would come from, it will take some time to get them delivered and get Polish crews trained to fly and support them. Poland flies the much more modern Block 52+ F-16C/D. While the type has much in common with earlier block Vipers, they are far from totally the same and would require specific training and logistical support to reach full operational capability in Polish hands.”
NATO equipment headache
Finally, Poland and NATO will need to worry about the equipment on the MiG-29 fleet operated by Warsaw. This is because Poland's MiG-29 jets have been upgraded with specific equipment such as radios, navigation and secure communication equipment to make them interoperable with NATO forces.
Transferring the jets to Ukraine would mean these components would likely have to be removed, given fears Russia could get hold of them.
PS: If Ukraine does get Poland's MiG-29 fleet, it would be the third operator of these jets! Germany gave the aircraft, inherited via East Germany, to Poland in 2003.