June 21 (Reuters) - The following are the top stories in the Financial Times. Reuters has not verified these stories and does not vouch for their accuracy.
Headlines
IAG and Ryanair plan EU legal challenge over air traffic strikes https://on.ft.com/2lkNmwu
Labour to give MPs free rein in Heathrow expansion vote https://on.ft.com/2Ic1Bga
Brexit casts shadow over Northern Ireland small business boom https://on.ft.com/2I6Mm8v
HS2 chief called to account over 'robustness' of budget https://on.ft.com/2MG3x46
Overview
Two British airlines, British Airways owner IAG and low-cost carrier Ryanair, are preparing a complaint to the European Commission over air traffic control strikes in countries like France that have led to 5,000 flight cancellations so far this year and breach Europeans' freedom of movement.
The UK's opposition labour party will give its members a "free vote" for the expansion of London's Heathrow airport, allowing Labour MPs to side with the Conservative government.
Enterprise Research Centre warns that the UK's exit from the EU customs union would hit growth of small business in Northern Ireland and the north of England.
HS2's chief has been accused of underestimating property purchases by up to 2 billion pounds ($2.63 billion), providing false figures in its budget and misleading parliament over the costs. ($1 = 0.7593 pounds)
(Compiled by Bengaluru newsroom; Editing by Sandra Maler)