LONDON (AP) — Shares in British Airways' parent company have tumbled after a catastrophic IT failure stranded thousands of passengers during a holiday weekend.

Shares in the International Airlines Group dropped about 3 percent in the first day of trading Tuesday after a weekend that saw hundreds of flights cancelled.

Shares in IAG, which is also listed in Madrid, had already fallen heavily in trading in Spain on Monday.

George Salmon, equity analyst at Hargreaves Lansdown, says that while BA is now running a full schedule, IAG is counting the cost of a calamitous weekend. Salmon says the cost of compensation and refunds could well run into the tens of millions.

Salmon says "the whole sorry episode has undeniably put a dent in BA's reputation for delivering a premium service."