DUBLIN (Reuters) - Ryanair RYA.I has been hit by strikes across Europe as it struggles in negotiations with trade unions, forcing it to cancel flights and hurting some of its bookings.

Aircrafts of low-cost airliner Ryanair are parked at the tarmac of Weeze airport near the German-Dutch border during a wider European strike of Ryanair airline crews to protest slow progress in negotiating a collective labour agreement at Weeze airport, Germany, August 10, 2018. REUTERS/Wolfgang Rattay

Ryanair pilots in Germany, Ireland, Sweden, Belgium and the Netherlands went on strike on Friday in the biggest one-day strike Europe’s largest low-cost carrier has faced.

Ryanair operates from 86 bases in 37 countries and carried 130 million passengers last year, making it Europe’s largest single-brand by that measure.

Below are a list of the strikes that have taken place or are planned since union negotiations began.

Aug. 10:

Ryanair faced its worst one-day strike after a walk-out by pilots in five European countries disrupted the plans of an estimated 55,000 travelers with the budget airline at the height of the summer holiday season.

Aug. 3:

Irish pilots staged a fourth one-day strike, causing Ryanair to cancel 20 flights. The airline has responded to the Irish action by cutting its winter fleet there by 20 percent and putting over 300 employees on preliminary notice. [L5N1UU456]

July 25/ 26:

Cabin crew in Italy, Spain, Portugal and Belgium staged a two-day strike that forced Ryanair to cancel the flights of more than 50,000 customers, the biggest strike to hit the airline at the time.

July 24:

Ryanair canceled 16 of around 2,300 daily flights on after the third one-day strike by Irish pilots.

July 20:

Ryanair canceled 24 of around 2,300 daily flights after a second one-day strike by Irish pilots.

July 12:

Around a quarter of Ryanair’s 350 pilots bases in its home country of Ireland went on strike for the first time in a push for better conditions.

March 29:

Ryanair canceled dozens of flights to and from airports in Portugal when cabin crew staged three one-day strikes on March 29, April 1 and April 4.

Feb. 10:

Three Italian unions representing mainly cabin and ground crew staged a four-hour strike because they were not included in contract negotiations with Ryanair.

Dec. 22:

Ryanair was unable to avert its first ever pilots strike on December 22 when pilots in Germany held a four-hour walkout but with little impact on flights.