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* EasyJet to follow Tui travel into Britain's top index
* Wood Group to drop out as energy services sector struggles
* LSE could replace Serco if it can hang on to 90th spot
* Thomas Cook surges 130 percent into probable mid-cap berth
By Alistair Smout
LONDON, March 4 (Reuters) - Airline easyJet is set to jointhe UK's leading share index for the first time and small captour operator Thomas Cook the mid-cap index as the tourismsector rebounds from tough trading conditions.
easyJet would follow in the footsteps of sector peerTui Travel, promoted to the FTSE 100 in December,and replace energy services firm John Wood Group.
The airline has risen 37.6 percent since the FTSE's lastrejig, in December, buoyed by rising passenger traffic and astrategy to boost revenue by offering extra services, with gooddemand for flights from London.
The imminent promotion reflects demand from leisure andbusiness passengers in the UK to travel abroad, which had beenmuted after the economic downturn, analysts said.
The surge in easyJet's shares has made it the 82nd biggestcompany in the UK by market capitalisation, overtaking TuiTravel, which was added at the last reshuffle.
Promotion to the FTSE 100 would further increase demand for2.5 million easyJet shares from those funds who passively trackthe performance of the index, Citi analysts said.
Also set to join the FTSE 100, the London Stock Exchange has risen 37 percent as trading volumes climbed andranks 90th by market cap, qualifying it for automatic promotion.
If successful, the former blue chip -- evicted from the toplist in June 2010 as trading volumes declined -- would probablysee demand for 1.8 million extra shares from index trackers,Citi said.
WOOD GROUP
John Wood Group -- set to leave the FTSE 100 afterdropping to 112th place by market capitalisation -- reflectsweakness in the energy services sector.
Any blue chip that closes at 111th place or below on Tuesdayevening automatically drops out of the FTSE 100, and if WoodGroup is demoted, index trackers could look to sell 3.6 millionshares of the group's shares, Citi said.
Only re-admitted into the top tier in September, Wood Grouphas underperformed in line with the rest of the sector and isdown 1.8 percent since the last reshuffle.
The stock was hit by a poor 2013 outlook, echoing falls forpeers Saipem and Petrofac.
Mid-cap outperformance has also brought outsourcing firmSerco to the cusp of a FTSE 100 exit. It is 110th in themarket cap list despite rising 6.4 percent since the last rejig.
While not in line for automatic relegation, it would bedemoted to make way for the LSE as things stand.
A Serco demotion would likely see the 2.5 million sharesdemanded by trackers of the FTSE 250 heavily outweighed by the7.5 million looking to be sold by FTSE 100 trackers, Citi said.
Serco, which makes around a fifth of its sales in the UnitedStates, has been hit by concern about potential outsourcing cutsthere as well as slow growth in the UK.
Serco and John Wood Group both report results on Tuesday, somay be saved if their shares get a big enough lift.
Mirroring the success of easyJet in gaining index promotion,Thomas Cook is in line to join the FTSE 250 after itsurged 130 percent since the last shake-up.
The firm cut its quarterly operating loss last month. Itsaid its turnaround plan was on track and that it had seenstronger operating performances in its major markets includingthe UK.
Also in line for an upgrade are online betting firm 888Holdings and NMC Health, while Stobart Group, JD Sports and Raven Russia could losemid-cap status.
