Aviation authorities have launched an investigation after airline pilots reported spotting an unidentified "large drone" flying at 6,000ft over the Irish Sea on Tuesday afternoon, amid widespread flight disruption caused by a National Air Traffic Services (Nats) computer failure.

According to air traffic control transmissions reported by the Irish Times, pilots on an Aer Lingus flight from Cornwall to Dublin sighted the drone approximately three kilometres to the left of their aircraft off the coast of County Wicklow at 5:20pm. AirNav Ireland confirmed that a safety report had been filed and passed to An Garda Síochána, who issued temporary airspace restrictions around Dublin shortly afterwards.

The incident occurred as Nats chief executive Martin Rolfe said he took responsibility for safety and restoring services following the outage. Mr Rolfe is due to meet Transport Secretary Heidi Alexander on Wednesday before she addresses MPs in the House of Commons during the second reading of the Civil Aviation Bill.

Severe knock-on disruption is expected to continue through Wednesday across major hubs including Heathrow, Gatwick, Manchester, Stansted, Birmingham, Edinburgh and Belfast, with thousands of travellers caught in backlogs and delayed on aircraft.

Flight tracking service Flightradar24 reported that total cancellations exceeded 1,000 on Tuesday evening. By 5pm, easyJet had cancelled 137 flights, British Airways 111, KLM 26, Eurowings 22 and Ryanair 21. Ryanair reported that more than 65,000 of its passengers suffered delays alongside 50 cancellations.

British Airways warned that operational disruption will continue through Wednesday at least, and confirmed it is offering affected passengers free rebooking options until Friday. European air traffic manager Eurocontrol said inbound flights had been held at airports abroad, with knock-on delays spreading across the continent.

Nats stated that it faces a "very complex recovery" after the technical glitch, which began at around 1pm on Tuesday and took nearly four hours to resolve. Airlines have demanded an overhaul of the system, pointing out that this is the third large-scale air traffic control stoppage in just over three years.

Alongside the travel disruption, wholesale gas prices have continued to climb. The month-ahead UK gas price rose by around 1% to reach 184p a therm, remaining close to Monday's peak, which marked the highest level recorded since January 2023.

The rising price is putting acute pressure on European nations working to replenish natural gas reserves before winter, making the target of filling storage facilities substantially more expensive. I will continue to track both of these developing stories and provide updates as further details emerge.