The blue-chip FTSE 100 index was flat. British airways owner IAG slipped 2% after Britain removed Portugal from its quarantine-free travel list, and added seven more countries to its red list.
Other airlines including Ryanair Holdings, Wizz Air and EasyJet fell between 1% and 2.4%.
The domestically focused mid-cap FTSE 250 index inched 0.1% higher.
Asian shares tracked Wall Street lower as signs of a firming U.S. economy stoked worries about higher inflation and an earlier withdrawal of Federal Reserve stimulus.
All eyes are now on the U.S. non-farm payrolls report for May due later in the day.
Among other stock, Reckitt Benckiser Group gained 1.3% after HSBC raised its price target on the stock. Reporting by Devik Jain in Bengaluru; Editing by Subhranshu Sahu