The chief executive said the airline has put in place “a number of measures” to prevent a repeat of the chaos during the Easter and anniversary periods, when thousands of flights were cancelled. Summer break for most schools in England and Wales starts this week.
Schedule discounts in the airline industry will “help”, but factors “out of our control” could affect flights, Mr Lundgren warned.
In an interview with the PA news agency at the Farnborough Air Show in Hampshire, Mr Lundgren said: “We operate up to 1,700 flights a day.
“We are doing it at the level of operational performance that you would have seen in 2019.
“But that being said, we cannot guarantee that there will not be things that are beyond our control that could affect our customers, as they also affect the customers of other airlines.
“We are absolutely focused on this. This is the number one priority for us, beyond the overriding objective of delivering a safe operation.”
Mr Lundgren said one of the main risks to reliability is that air traffic control providers impose restrictions.
“It only takes one or two people in the tower to be sick and then power restrictions come into play,” he said.
“Flow restrictions can ultimately lead to cancellations.”
Asked if he is concerned that some passengers could transfer to Ryanair, which has not canceled as many flights in recent months, Mr Lundgren replied: “Every airline has had cancellations.
“We sincerely apologize for the events that took place when we faced day-to-day challenges.
“But we have taken the right actions to correct that and hope to continue to deliver a great operation for the rest of the summer.”