Comment by mrandish

> I would imagine it's incredibly expensive to maintain.

Everything that flies is expensive to maintain but the costs to maintain most older aircraft tends to be much lower than new ones, sometimes even if certain unavailable parts need to be rebuilt or fabricated. Part of the difference is newer designs tend to use advanced composites and manufacturing techniques which can yield increased performance and efficiency but are expensive and often require specialized techniques to service/replace.

The second factor is that funding, designing, validating and manufacturing new military aircraft platforms has grown astronomically expensive for a huge number of reasons.