Airfields and Aircraft Factory numbers:
| Type | Duration | Refuel | Cost | HP |
| Field 1 | 2 Hours | 30 mins | 1500 | 20 |
| Field 2 | 4 Hours | 20 mins | 2000 | 60 |
| Field 3 | 8 Hours | 10 mins | 2650 | 120 |
| Factory 1 | 30 mins | 30 mins | 3600 | 20 |
| Factory 2 | 4 Hours | 25 mins | 4800 | 40 |
| Factory 3 | 12 Hours | 20 mins | 6400 | 80 |
| Factory 4 | 24 Hours | 15 mins | 8550 | 120 |
| Factory 5 | 32 Hours | 10 mins | 11350 | 160 |
If you're just making them for the refuel, absolutely go normal airfields. but the 30 construction time for the factory is very nice. Even if you have resources to burn, that cost difference is massive, and it would also take significantly longer to get factories online.