London market ended the session on a marginally negative note on Wednesday (14 December), as news of a possible strike over the festive period at British Airways took its toll on owner IAG's shares.
The FTSE 100 closed 0.28% or 19.38 points lower at 6,949.19, while the FTSE 250 ended the session 0.19% or 33.24 points lower at 17,682.38, as the market's attention shifted to the US Federal Reserve with analysts pricing in a rate hike of 0.25%.
In the immediate aftermath of Donald Trump's win, the prospect of the Fed going ahead with its planned rate hike this month looked far-fetched but the US economy has since improved markedly, meaning Janet Yellen is expected to deliver an upbeat message.
"While a rate hike is almost entirely priced in, the Fed's expectations for the year ahead will be key, with markets currently remaining quite cautious on further increases next year," said Oanda's senior analyst Craig Erlam.
Meanwhile, IAG grabbed the market short-sellers' attention for all the wrong reasons with one of its flagship airlines British Airways facing the prospect of strike action.
In a statement, the Unite union said 79% of the more than 2,000 workers who were balloted voted in favour of the action, which will take place at London Heathrow Airport and could begin after 21 December.
The union, which is yet to confirm the dates hit by the strike, has urged Britain's flagship airline to return to the table for further negotiations, after cabin crew personnel rejected the offer for a 2% pay rise.
On the back of the news, IAG's shares ended the session 2.82% or 12.60p lower at 433.90p, with airline group finding itself among the biggest FTSE 100 fallers, alongside Dixons Carphone (-6.57%), Barclays (-2.63%), Antofagasta (-2.37%) and Mondi (-2.15%).
Going the other way, Polymetal International (+6.41%), Capita (+5.42%), Micro Focus (+4.18%), Fresnillo (+3.51%) and Whitbread (+3.15%) were the biggest blue chip gainers.
Meanwhile, spread-betting firms' recovery continued at pace, following on from a huge selloff after UK regulator the Financial Conduct Authority called for stricter regulation of the industry on 6 December.
Market leaders IG Group (+7.88%) and CMC Markets (+5.16%) were among the biggest FTSE 250 risers, alongside Paysafe Group (+8.11%), Hastings Group (+6.82%) and International Personal Finance (+4.80%).
Among the biggest fallers were JD Sports (-7.08%), Thomas Cook (-4.67%), Sports Direct (-3.81%), BGEO (-3.45%) and Greencore Group (-3.22%).