Police at Gatwick Airport were not prepared for an attack by more than one drone, a senior officer has said.
Flights were suspended for 30 hours after the drone sightings in December, causing chaos for 140,000 passengers.
Sussex Police Supt Justin Burtenshaw said its “drone plan” had been based “around a single drone incursion and not a multiple one”.
He said the airport industry was left “playing catch up”, but Gatwick’s defences were “now fit for purpose”.
“We have now got the mitigation technology in place, I wish we had that in December,” he added.
Supt Burtenshaw was speaking to Philip Ingram, a former British Army intelligence officer, at the Interpol World conference in Singapore on 3 July.
He said: “We had a number of witnesses who saw two drones at the same time, so we’re happy that on at least a couple of those occasions there were two drones flying.”
No-one has been charged over the disruption, described as a “sustained” drone attack.
Supt Burtenshaw said this was a “reflection of how complex it is” and was “certainly not a failing in my officers”.
The officer also said that “jamming technology” – intended to remotely bring down a drone – was “just not tested”.
“All this stuff is built for theatre of war. We are introducing something that is great in a desert into an urban environment and saying we are not quite sure what it’s going to do,” he said.
“I still don’t know what effect a jamming technology is going to have on a hospital that is four kilometres away, so we have to be really careful.”
Supt Burtenshaw said the technology, which was installed in January at a cost of £5m, would only be used if there were “no aircraft in the sky”.
He added: “[It’s] not something we would use very quickly.”
Footage of Supt Burtenshaw being interviewed by Mr Ingram had been uploaded on YouTube, but was removed after a journalist contacted Sussex Police.
The force said the interview had been carried out “on the understanding that it would be shared only among those attending the private conference”.
It added: “Once the organisers realised their error in broadcasting the interview on YouTube, they removed it.”