Yellow-and-blue fighter jets sit neatly lined up on the tarmac at the air force academy in Libya's Misrata, no longer awaiting students but orders for strikes against the Islamic State group.

The military college has been transformed into a major base in the battle against the Islamist militants since they gained ground in the country in the turmoil that followed the 2011 uprising.

For a year and half its planes -- flown mainly by former instructors in their 40s and 50s -- have been carrying out strikes against IS group, and for several months they have been targeting what was their main stronghold in North Africa.

IS group took over Sirte some 250 kilometres (150 miles) east of Misrata in June last year, sparking fears the Islamist militants would use the Mediterranean city as a launchpad for attacks in Europe.

Forces loyal to the UN-backed government this June fought their way into Sirte and have since pushed back IS fighters into one last district of the city.

At the air force academy in Misrata, two pilots board a fighter jet don their helmets and wait for the signal to fly off on a reconnaissance mission of IS targets.

"We know this terrorist organisation operates worldwide," Brigadier-General Rajab Abdaraheem says, referring to IS.

"When I'm up in the air about to hit an IS target, I feel like I'm defending my country and the world," says the 57-year-old pilot who has been flying since he graduated in 1982.

Since it opened in 1975, more than 30 classes of around 1,000 trainee pilots have graduated from the academy.

The school trained officers from Libya and other countries in the Arab world until the 2011 uprising that toppled and killed longtime leader Muammar Gaddafi.

The academy saw heavy fighting between the rebels and fighters loyal to Gaddafi and was damaged in NATO strikes backing the opposition who retook the area.

The door of the main maintenance hangar at the academy is still peppered with bullet holes.

After 2011 "we renovated the facilities... but when the situation in Libya didn't stabilise the academy became a (military) base," says Brigadier-General Abderahman Mohammad.

Officers -- most of whom had graduated for the academy in the 1980s and 1990s -- transformed the college's training aircraft into warplanes, equipping them with rockets and missiles, they say.

The aircraft date mainly from the Gaddafi era and include some two dozen ageing jets including Russian-made MiG-23s, Yugoslav Soko G-2 Galebs and Czech L-39s, as well as helicopters.

Beyond the tarmac, dozens of empty wooden boxes that used to contain missiles lie empty in the dust.

The base's forces "quashed any fantasy IS might have had, prevented it from expanding and limited the movements of its members," says Mohammad Qanono, a spokesman at the airfield.

Since March last year -- when the first jet took off from the base on a mission against IS -- until Sunday, the academy's planes had carried out 1,400 sorties on missions to survey and strike IS targets, he says.

Around 600 of those missions have been logged since May and were mostly against IS positions in Sirte and in the desert to the south of the city.

Since the battle for Sirte began on May 12, pilots at the base have also been tasked with ferrying out wounded loyalist fighters in helicopters to the Misrata hospital.

More than 400 fighters loyal to the Tripoli-based government have been killed and about 2,500 wounded since the start of the offensive.

And since the start of last month, forces backing the Government of National Accord have also been supported by US air strikes.

On Friday, the United States Africa Command said that since the US campaign began on August 1, US drones, helicopters and bombers had carried out a total of 108 air strikes against the militants in Sirte.

"We asked for... US air strikes because the US air force is very precise," says Qanono.