The regime has also increased its use of military and civilian transport aircraft to deliver supplies to its forces in the north. These aircraft can use the airports of Aleppo, Rasin el Aboud and Jirah to deliver their supplies. Mi-8 helicopters staging from these airports are also reportedly being used to resupply the isolated and surrounded regime outposts scattered across the Aleppo and Idlib governorates. Resupply from the air is far more costly and inefficient than resupply from the ground, and there are limits to what can be delivered by air. These issues are compounded by the Syrian Arab Air Force's dearth of serviceable transport aircraft.
Though it is a less than optimal solution, the regime can likely continue resupplying its forces in Aleppo using air transport and the eastern route. However, both these options are also being threatened by advancing rebel forces. Having seized the town of Tel Abyad in the Ar Raqqah governorate, the rebels are now determined to move south and take Ar Raqqah. Ar Raqqah has been largely untouched by the fighting, and large numbers of refugees from places such as Aleppo, Homs and Deir el-Zour have fled to the city. There are fears in the international community and among many Syrians that a rebel advance on Ar Raqqah would put these refugees at risk, but the rebels are adamant that the city is critical to their war effort. Indeed, the seizure of Ar Raqqah and neighboring Al-Thawrah would cut the eastern land route to Aleppo.
The rebels also have increased their targeting of airports and air bases used by the regime to launch airstrikes and deliver supplies. Besides the Abu Duhur Air Base that is already under siege, rebels in Aleppo have made several attempts to advance on the Aleppo airport, and rebels in technicals — likely staging from al-Bab — have attacked the Rasin El Aboud airport to the east.
Logistics are a critical factor in any conflict, and if the regime forces in Aleppo find themselves cut off from supply, they would be able to hold out only as long as prepositioned supply stocks lasted. The regime may yet make a concerted effort to keep its supply lines open, but this would likely require a considerable diversion of forces from the capital, leaving Damascus even more vulnerable to rebels in the area. If the rebels are able to sever supply lines to regime forces in Aleppo and trap them there, a considerable portion of the regime's forces would be at risk of being captured or killed, creating an opening for substantial rebel offensives into the south after the regime pockets are reduced.