The purposes of air support are reconnaissance, tactical strikes and to support ground troops.
Denying reconnaissance results in (a) that side committing larger forces to pitched battles making destruction of the opponent more likely and (b) not committing enough of the right forces to pitched battles resulting in greater losses (one intention of the no fly zone). It also increases the likelihood of successful assaults on those denied aircract.
Tactical strikes allow the destruction of tanks, opponent HQs and leaders, supply dumps and key infrastructure. These actions lead to a shortening of the conflict. Preventing these actions increases theneed for land-based assault using tanks, machine-guns and infantry against one another. Destruction is more wide-spread, more troops are needed to be killed. More homes, hospitals, schools, offices and business are destroyed as towns need to be flattened.
Without air support, warfare is more akin to the kind of close combat massacres that occurred up to the Great War.
When the great powers impose a No Fly Zone “for humanitarian reasons” it results in a longer war, greater destruction of infrastructure, more deaths, more civilian deaths, more trauma, more widows and orphans, more refugees, more cost to aid agencies, more influx of external combatants, more civilians becoming armed and involved.
The imposition of a No Fly Zone is not ‘humanitarian’; it is a cruel and cowardly way of manipulating the outcome of an internal conflict for poitical ends with wanton disregard for the suffering caused.