Hong Kong/Sydney, July 1 (Reuters) - Asian airlines, which attracted more passengers and raised ticket prices on European routes following the outbreak of the Iran war, are beginning to lose those advantages as Gulf carriers resume flights and offer lower ticket prices, data suggests.

This shift came gradually, but it raised doubts about the ability of airlines, including Singapore Airlines, Cathay Pacific Airways, Korean Air and ANA Holdings, to retain a large portion of the market share they gained during the period of turmoil.

Data from SEREEM showed that Emirates, Qatar Airways and Etihad Airways carried about a third of passengers from Asia to Europe, and more than half of passengers from Australia and New Zealand to Europe, before the outbreak of war.

Major airports in the Gulf were shut down as Iran’s war broke out on February 28 due to drone and missile attacks, but air traffic had recovered by mid-June to about 90 percent of its normal levels, according to Flightradar24 data.

According to data from the International Air Transport Association (IATA), between March and May, Middle Eastern airlines saw a marked improvement, recording a 28 percent decrease compared to about 60 percent a year earlier.

While the number of passengers on direct flights from Asia to Europe rose by about 30 percent year-on-year in March, this increase had slowed to 15 percent by May.

A Korean Air spokesman said the company recorded a year-on-year increase in seat occupancy rates on its flights to Europe between March and May, but demand declined as Gulf carriers resumed operations during the second quarter.

ANA Holdings, which has not yet released its May data, said its European flight seat occupancy rate fell from 93.1 percent in March to 86.9 percent in April, but remains about 8.7 percentage points higher than the same period last year.

Cathay Pacific reported that its seat occupancy rate across its network rose in May by two percentage points year-on-year to 86.8 percent, compared to a 9.5 percentage point increase in March to 92.2 percent.

Independent aviation analyst Brendan Sobie said the data points to a gradual rather than a sudden rebalancing, noting that Singapore Airlines' performance clearly illustrates this trend.

The airline's seat occupancy rate on European flights rose 13.8 percentage points in March, but gains narrowed sharply to 4.9 points in April and just 1.1 points in May.