The UK airport operator BAA is to take court action against Ryanair over what it claims is non-payment of £1 million (1.5 million) landing fees at Stansted Airport, it announced yesterday.

However, Ryanair responded by saying it has issued its own proceedings against BAA "for over-charging on fuel levies at Stansted over a 12-year period".

BAA said a High Court writ was issued against the carrier after a 4 p.m. deadline yesterday was not met. Ryanair, along with other carriers, gets a special airport-charging discount from BAA as part of BAA's expansion of Stansted.

Ryanair, which handled 12.5 million passengers at Stansted last year, will still be able to operate from the Essex airport but its charges could now nearly double.

A Ryanair statement last night said: "As BAA is aware, our agreement on charges is very specific and expires in 2007."

The level of subsidies enjoyed by the carrier for using Charleroi Airport in Belgium fell foul of the European Commission which imposed a 2.74 million fine on Ryanair. The airline has launched an appeal against the fine.

Market sources in Dublin last night said that, if BAA decided to raise landing charges, it could significantly push up costs for Ryanair. According to some analysts, such a move could cost the airline £16-£24 million each year.

Analysts at NCB Stockbrokers remained upbeat on the stock last night however, describing Ryanair as "solid" over the longer term. Ryanair will issue first-quarter results at the start of next month.