The FTSE Russell’s latest quarterly review, published after markets closed on Wednesday, is set to trigger significant activity in the coming days as investors prepare for index changes scheduled to take effect on September 21. The review determines which companies are promoted to or demoted from the FTSE 100 and FTSE 250 indexes, influencing the flow of investment, particularly from passive index funds.

One of the most notable developments is the return of budget airline easyJet to the FTSE 100, just six months after its demotion to the FTSE 250. The airline has recently been the focus of a bidding contest between investment firms Apollo and Castlelake. Castlelake withdrew last month after Apollo submitted a higher bid to acquire easyJet at 715 pence per share. The takeover is expected to be completed by the first quarter of 2027, at which point easyJet would become privately held and delisted from the London Stock Exchange. Meanwhile, easyJet’s shares rose modestly by 0.6 percent to close at 673.25 pence on Wednesday.

Joining easyJet in the top tier will be Ithaca Energy, an oil and gas company active in the North Sea, holding a 20 percent stake in the Rosebank field. The field awaits regulatory approval to begin production, anticipated in the first half of 2027. Ithaca’s shares gained 2.3 percent to settle at 286 pence, buoyed in part by a 0.8 percent increase in Brent crude prices, which ended the day at $95.35 per barrel.

Despite these gains, the FTSE 100 index closed lower, declining 32.83 points, or 0.3 percent, to 10,756.45. The FTSE 250 also saw a downturn, falling 197.23 points, equivalent to 0.8 percent, finishing at 24,324.06.

Among those making way for the new entrants in the FTSE 100 are companies like Entain, owner of Ladbrokes and Coral, which recorded a slight increase of 0.5 percent to 517.5 pence, and housebuilder Persimmon, which fell 1 percent to £11.38. A notable exit from the FTSE 250 was Aston Martin Lagonda. The luxury car manufacturer’s shares edged up 3.5 percent to 34.5 pence but have declined sharply since its 2018 initial public offering at £19.

Meanwhile, market sentiment remains cautious amid concerns over inflation, government debt levels, and the economic impact of the ongoing conflict in the Gulf region. However, U.S. markets experienced a midweek rebound following two days of losses, with technology stocks leading the recovery. Nvidia shares rose 3.3 percent, and Micron Technology climbed 2.4 percent. The Nasdaq Composite index increased by 118 points, or 0.5 percent, to 26,217.83, while the S&P 500 added 35 points, also 0.5 percent, reaching 7,666.60. The Dow Jones Industrial Average gained 295 points, or 0.6 percent, closing at 53,061.95.