Blue chip shares slipped in afternoon trading (6 October) after budget airline easyJet warned that the weak pound would cost it £90m (€101, $114m) this financial year.
EasyJet blamed the falling price of sterling since the Brexit vote for the shortfall, adding that its annual pre-tax profits would come in at between £490m and £495m, well below the £686m it posted last year. Sterling has fallen as much as 15% since the EU referendum.
The FTSE 100 Index fell 9 points to 7024.4, as shares in a range of travel stocks fell after the carrier's update. The FTSE 250 fell 52.3 points to 18148.2.
EasyJet said it had gone through an "extraordinary" year that also included terror attacks and a summer price war sparked by rival Ryanair.
The sector is struggling with overcapacity and weakened demand caused by terror attacks in Brussels, Paris, Nice and Turkey. Shares in easyJet fell 60p to 943p.
IG market analyst Joshua Mahony said: "The feeling is that this could be just the beginning for a firm which is expecting to suffer at the hands of June's referendum result."
British Airways owner IAG fell 10.2p to 386.4p, while in the second tier Thomas Cook slipped 1.2p to 71p.
In afternoon trading the biggest risers in the FTSE 100 Index were GKN (+6p to 337.2p), TUI (+17p to 1131p), ITV (+2.8p to 186.5p), Royal Bank of Scotland (+2.6p to 186.4p) and Rolls-Royce (+9p to 763.5p).
The biggest fallers in the FTSE 100 Index were easyJet (-60p to 943p), Marks & Spencer (-13.5p to 324.2p), Smith & Nephew (-45p to 1220p), IAG (-11.2p to 385.6p) and Capita (-18.5p to 637p).
In afternoon trading the biggest risers in the FTSE 250 Index were BTG (+30p to 677p), Tullow Oil (+10.4p to 272.2p), William Hill (+4.4p to 310p), CLS Holdings (+22p to 1567p) and DS Smith (+5.3p to 397p).
The biggest fallers in the FTSE 250 Index were Dunelm Group (-37.5p to 820p), Countrywide (-8.4p to 208p), Ted Baker (-98p to 2444p), Mitchells & Butlers (-8.7p to 271.1p) and Restaurant Group (-11.8p to 368.6p).