easyJet and Ithaca Energy will join the FTSE 100 at the September 2026 quarterly review of the FTSE UK Index Series, while Entain and Persimmon drop into the FTSE 250. The changes were confirmed by FTSE Russell and will be implemented at the close of business on 18 September 2026, taking effect from 21 September.
easyJet returns to the blue-chip index six months after its relegation to the FTSE 250. Its promotion may prove brief: the airline has agreed a takeover by a private equity buyer valuing it at about 5.7 billion pounds, a deal that would ultimately remove it from public markets altogether.
Ithaca Energy, a subsidiary of the Israeli Delek Group, joins after a strong run in which its shares have risen roughly 64 per cent so far this year. Its growth pipeline includes a 20 per cent interest in the Rosebank field, which remains subject to regulatory approval with first oil targeted for the first half of 2027.
The two departures reflect a harder year. Entain, the betting and gaming group, has seen its share price weaken by about 30 per cent since the start of the year. Persimmon, one of the largest British housebuilders, is down roughly 16 per cent over the same period, with the UK housing market still absorbing higher borrowing costs.
Quarterly reshuffles are mechanical, driven by market capitalisation rankings rather than judgement, but they are a useful read on where the market's centre of gravity is shifting. This round moves the index further toward energy and travel and away from consumer-facing gambling and housebuilding, two sectors carrying the brunt of weaker discretionary spending and higher rates.
There are practical consequences for the companies involved. Index membership drives passive fund flows, so promotion brings automatic buying from tracker funds and relegation the reverse, and it changes the visibility a company has with institutional investors. For boards, an index move is also a governance moment: it resets the peer group against which pay, disclosure and performance are benchmarked, and it often precedes changes in the shareholder register and, in time, in the leadership team.
