This year’s earlier timing of Easter resulted in a 0.7% decline to 5.8 million passengers using Heathrow in April.

Combining the two months to take into account the ‘Easter effect’, traffic was up 1.6% over the same period in 2012, according to Heathrow.

The airport continued to see an increase in aircraft size, with the average number of seats per aircraft up 2.7%.

The average number of passengers per flight remained at 150.9, resulting in an average load factor of 74.3%, a reduction of 2.1%.

Despite the lower passenger numbers, European traffic was resilient, up 1.4%, driven by rises to Italy (9.7%), France (9.9%), and Norway (22.5%).

North America traffic was down 1.3% in the month, while traffic to the BRIC economies was up 1.8% overall. China saw the biggest gain, up 12.1% and traffic on Indian routes rose by 3.2%.

Heathrow warned that the Civil Aviation Authority’s proposed price cap proposals for the period between 2014 and 2019 would discourage continued investment.

Chief executive Colin Matthews, said: “The record customer satisfaction scores achieved last quarter are a result of joint work with airlines and our strong investment.

“We want to keep making Heathrow better for our passengers and airlines by continuing to invest.

“We operate in a global competitive market for debt and equity capital, and the CAA must set the allowed returns at a competitive level in order for those investments and improvements to continue.”

Heathrow Airport Holdings reported a 0.4% rise in passengers used Glasgow airport in April to 549,00 while Aberdeen numbers were up by 3.7% to 284,000. Those using Southampton dropped by 1.8% to 136,000.