London's main index inched up on Monday as rises in banking shares outweighed the impact of a profit alert from Germany's Lufthansa on airlines, while UK contractor Kier Group skidded to an all-time low.
Both the FTSE 100 index and the FTSE 250 midcap index ended 0.2% higher.
With the spotlight on Wednesday's US Federal Reserve policy decision, the banking index broke a four-day losing streak with a 0.9% rise, led by Asia-exposed banks including HSBC and Prudential after Hong Kong's leader backed down over an extradition bill that has sparked mass protests.
"It's hard to recall a time we headed into an FOMC meeting with so much at stake and with so much uncertainty about what might be agreed," Markets.com analyst Neil Wilson said.
"Traders may start to show some nervousness ahead of the Fed meeting if they think it won't be accommodative as hoped."
The Fed is expected to leave interest rates unchanged but potentially lay the groundwork for a cut later this year as a prolonged trade war with China puts more strain on the US economy.
The Bank of England also meets this week, with little expected but all eyes on central bank policymaking globally after two weeks in which hopes of policy easing have driven a stock market recovery from losses in May.
EasyJet and British Airways owner IAG gave up 4.4% and 2.2%, respectively, on the main bourse after Lufthansa cut its 2019 profit outlook due to competition from low-cost rivals in Europe.
Mid-cap component Wizz Air also dipped 2.6%.
Kier, whose shares have plunged this month due to a report of a discounted sale of its unit and a profit warning, lost another 17.4%, reaching a new all-time low, after the builder suspended dividend, and announced divestment plans and 1,200 job cuts.
"The profit warning from Friday is still fresh in traders' minds, and even though today's restructuring scheme is a clear sign the firm is taking action, it still hasn't reassured investors," CMC Markets analyst David Madden said.
DS Smith slipped 5.1% on its worst day in over four months after Exane BNP Paribas downgraded the stock to "underperform" on worries about the plastic packaging firm's capital spending and exceptional costs.
Energy provider Centrica also tumbled to more than a decade low, ending 2.4% lower after Macquarie initiated coverage with an "underperform" rating.
Huatai Securities' GDR ended 3.7% higher on its first day of trading in what is Britain's first listing via the long-awaited London-Shanghai stock connect project.
Huatai, among China's largest brokerages, had earlier risen as much as 7.1% to $21.96 on the day.