Lucknow: The Sarojininagar police on Monday lodged an FIR against an unknown person for a hoax bomb threat scribbled on a tissue paper inside the aircraft lavatory.The action was based on the written complaint submitted by IndiGo’s security staff a day after a Delhi–Bagdogra IndiGo flight had to make an emergency landing in Lucknow after a hoax threat. FIR lodged by IndiGo security officer Vipin Tripathi reported that flight 6E-6650 received a mid-air alert at 8.45 am after a crew member found a handwritten note reading ‘Bomb on the plane’ inside the rear washroom. The pilot informed Air Traffic Control and diverted the aircraft to Lucknow, where it landed at 9.17 am and was moved to an isolation bay. Quick Reaction Teams, bomb disposal units, CISF personnel, and airport officials cordoned the area and conducted a detailed inspection. FIR states that the incident created panic and amounted to spreading a “dangerous rumour.” The aircraft was also carrying sealed radioactive medical material with proper NOC, prompting additional caution. Investigators later declared the threat a hoax, and the aircraft was cleared for departure to Bagdogra at 4.30 pm. Police have registered a case under Section 353 of the Bharatiya Nyaya Sanhita against an unidentified person and initiated further investigation.