The Airports Authority of India (AAI) has lodged a complaint with aviation regulator DGCA that the fighter aircraft entered into designated civilian airspace at noon on Monday.
Civil Aviation Ministry sources said the DGCA has sought inputs on the incident from the Air Headquarters, while IAF officials said they were "investigating the incident and the related allegations."
The incident is understood to have occurred when four fighter aircraft entered the "defined area", which is identified for civilian air traffic, without any information to or coordination with the Nagpur air traffic control (ATC), sources said. They remained in the civilian flight path for about 15 minutes.
The fighter jets were operating at 'flight level 230' which caters to civilian planes and were not in VHF (Very High Frequency) or radio contact with the ATC tower.
The incident, termed as "serious violation" by civil aviation authorities, could have led to a major accident as the Nagpur airport has a number of flights landing and taking off around that time, they said.
The AAI, which controls the airport, has recorded the incident and lodged a formal complaint with the Directorate General of Civil Aviation (DGCA). The DGCA has in turn referred the matter to the IAF Headquarters for their views, the sources said.