Flights could be disrupted after Brexit, the transport secretary has admitted, but he said the European commission would be to blame for not starting talks on a deal to keep planes in the air.

Chris Grayling told an aviation conference that disruption was “unlikely” but that talks to secure an aviation agreement had not yet started with only five months to the date of Britain’s departure. He added: “That process is not in our hands.”

Grayling said there was “no way that flights will stop” between the UK and the EU, but there appeared to be a marked change in tone from previous speeches in which he had described planes being grounded after Brexit as inconceivable.

Speaking at the Airport Operators Association annual conference in London, Grayling said: “It is theoretically possible that EASA [the European Aviation Safety Agency] could refuse or delay the certification of UK-certified planes. I think it is highly unlikely.”

The legal basis for continuing flights between the UK and the EU is unclear without a new deal. Grayling said the UK could fall back on bilateral agreements with individual EU member states but was hoping for a “barebones” aviation agreement with the whole bloc, saying he had not met “one single person” in the commission or a member state who believed there would be an interruption to aviation.

“I’ve offered the commission to prepare a barebones deal if there is no broader agreement,” he said. “They are not yet ready to begin but the commission has said very clearly it expects there to be an agreement.”

Asked if he would take responsibility for any disruption to aviation, having earlier dismissed industry warnings, the transport secretary said: “It’s not me that is not opening talks.”

Grayling said the Ryanair chief executive, Michael O’Leary, who has repeatedly claimed flights could be grounded, was “selling tickets for next summer and expanding the number of routes between the UK and the European Union”.

But airport bosses said they were preparing for the worst, including queues of lorries potentially jamming Britain’s main road artery, the M1, because of new customs requirements.

Karen Smart, the managing director of East Midlands airport, which handles large amounts of freight, said Brexit could cause tailbacks on the motorway if longer checks on goods lorries were needed.

She said the airport hoped pre-Brexit fears would be “like the Millennium bug” and prove unfounded but that it was working closely with local authorities to make contingency plans.

Referring to Operation Stack, the government plan for holding thousands of lorries on motorways leading to Channel ports, Smart said: “My biggest risk is an Operation Stack on the M1 because vehicles can’t get to the airport because the processes have been slowed down. We have thousands of vehicles that are processed through the airport.”

Derek Provan, the chief executive of AGS Airports, which owns Aberdeen, Glasgow and Southampton airports, said it needed certainty that there would be no disruption, adding: “Unlikely is not much good.” He said the airports were spending a lot of time and money on post-Brexit contingency planning.

Ed Anderson, the chairman of the Airport Operators Association, said a framework agreement was needed swiftly to give passengers the confidence to book flights for next summer. “We are concerned at the lack of progress in this aspect of the Brexit negotiations,” he said.