Gadhafi's warplanes give him an extra edge in the fight against rebels. At the very least, they intimidate rebel fighters battling in open desert with little cover.
Still, so far Gadhafi has not brought — or not been able to bring — the full firepower of the air forces against the rebellion. In Sunday's fighting, the massive artillery and rocket bombardment did more to break the rebel ranks.
That may be in part because of the weakness of his air arsenal and worries over the loyalty of its personnel. Over the decades, Gadhafi built a large air force, estimated at around 500 combat aircraft and helicopters. On Google Earth, dozens of Soviet-era MiG and Tupolev fighters can be seen lined up at air bases in Sirte and in the deserts of the southwestern part of the country.
But well over half of the aircraft are believed to be unable to fly, because they are outdated and because under decades of sanctions Libya was unable to procure spare parts, according to GlobalSecurity, a U.S.-based website that monitors world militaries. Several years ago, Libya signed a deal with France to repair its 1970s-era French Mirage fighters, but only four of them were brought up to speed.
But air activity does seem up the last week or so. I assume that Khaddafi has brought in Russian mercenaries or others with experience in maintaining the old birds that Libya has lying around in disrepair. Perhaps even contract pilots are flying missions.
It wouldn't take too much to throw up an air defense of some sort for the rebels by sending in mercenary/contract technicians to bring rebel-controlled air defense missiles online. Surely some have fallen into rebel hands in the east. They could be repaired.
Just by being targeted by some missiles, pilots flying for Libya will be more cautious and less accurate in bombing. Shoot a couple down and pilots might not fly over defended targets at all. This would be cheaper than intervening in the civil war by declaring and enforcing a no-fly zone.
UPDATE: I would like to clarify a mistaken notion that has gained ground with those opposed to enforcing a no-fly zone. That is, there seems to be a growing consensus from Secretary Gates down to pundits and reporters that a no-fly zone requires us to take out ground-based air defenses. In a decade of no-fly zones over Iraq, we did not carry out a campaign to destroy air defenses. When Saddam's gunners shot at us, we often took the opportunity to bomb them (and as the air defenses got closer to mosques and schools we started dropping concrete smart bombs to avoid collateral damage), to be sure. But knocking out all the air defense systems (missiles and radars and what not) was not a requirement for enforcing a no-fly zone.