An Air India flight from Frankfurt to Delhi was diverted to Jaipur on Wednesday after air traffic control (ATC) received a hijack alert for the aircraft. Officials said the pilot told ATC there was no hijacking, and ATC asked him to divert to Jaipur. The Directorate General of Civil Aviation (DGCA), India’s aviation regulator, will examine the ATC system for a possible technical error.
Flight AI 2030, a Boeing 787-9 with 306 people on board, landed safely at Jaipur and was moved to an isolation bay for security checks. According to people aware of the incident, the aircraft was briefly squawking transponder code 7500, the internationally recognised aviation code for hijacking or unlawful interference.
Airline and DGCA officials, speaking on condition of anonymity, said the flight was diverted on ATC’s instructions. The airline officials also said the pilots had made no mistake.
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Air India flight resumes journey to Delhi
The aircraft was cleared to fly on to Delhi. It took off from Jaipur at 2.37pm and landed in Delhi at 3.11pm. In a statement, Air India said the flight was diverted “following a perceived security concern”, and that security agencies had checked and cleared the aircraft and crew.
A passenger told HT that one of the pilots spoke to passengers about 30 to 40 minutes before the scheduled landing in Delhi, as the crew was preparing to begin descent from cruising altitude.
“He said he didn’t know why, but he had been asked by ATC to divert to Jaipur and land there. He said he’d keep us updated,” said Swasti Rao, a professor at OP Jindal Global University and a consulting editor at The Print. Officials separately confirmed that the pilot told passengers the diversion was on ATC’s instructions.
The crew came back on almost every 10 minutes after that, she said, telling passengers they were landing at Jaipur and were in touch with Delhi ATC. After landing, the pilot came back on the public address system. “I didn’t want to panic anybody, but there was a hoax,” Rao quoted him as saying.
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How aircraft transponders work
A transponder is a radio receiver and transmitter on board an aircraft. It answers a ground radar’s ping with a four-digit code, which lets controllers tell one aircraft from another on their screens. Pilots and controllers call sending that code “squawking”. Each digit runs from 0 to 7, which allows 4,096 codes.
In India, controllers assign each departing flight its own code. International flights entering Indian airspace keep the code they were using in neighbouring airspace, and an aircraft without an assigned code sets 2000 before it enters.
Three codes are reserved worldwide: 7700 for an emergency, 7600 for radio failure and 7500 for unlawful interference, which covers hijacking. Under US rules, controllers never assign 7500 unless the pilot has first reported unlawful interference.
On the Boeing 787, pilots set the code through tuning and control panels (TCPs) on the flight deck’s centre console. These are units with a display and a keypad, which crews also use to tune radios and navigation aids. A pilot selects the transponder page and keys in the four digits. Controllers tell the crew which code to set, usually over the radio, and the crew enters it.
Aircraft also broadcast their transponder code through ADS-B, a system in which an aircraft transmits its own position and status, and public flight-tracking sites pick up those broadcasts.
Wednesday’s case was similar to a January 2025 incident when a Mumbai-bound Air India flight, which had just taken off from New Delhi’s Indira Gandhi airport, sent an emergency signal to air traffic control (ATC) in the Capital, suggesting it had been hijacked. The pilot later informed the ATC that it was a false alarm.
A possible glitch
“The DGCA will investigate the ATC system for a possible technical error,” an official said, asking not to be named.
A former bureaucrat offered one possible explanation, which he described as a hypothesis. “One possible explanation is a technical anomaly within the system that generates or assigns transponder codes, potentially involving multiple aircraft operating in close proximity during military formation flights. Aircraft may be assigned different codes, such as 7511, 0011 or 5600, and a system-level glitch could theoretically result in an unintended code combination that this time produced 7500, the internationally recognised hijack alert code. Similar anomalies have occurred previously, but they never resulted in the generation of 7500, thus not attracting this level of attention. However, this remains a technical hypothesis and would require verification through a detailed examination of the system, flight data and ATC records,” he said.
India’s published air traffic rules say the pilot of an aircraft subjected to unlawful interference should try to set the transponder to 7500. Under international procedures, controllers who see the code do not mention unlawful interference on the radio unless the pilot does so first. They ask the crew to confirm the code, and India’s rules treat a pilot’s silence as confirmation that the code was set deliberately.