All passenger flights at Berlin Brandenburg Airport were canceled on Wednesday after a warning strike by the Verdi union affected 57,000 travelers.Around 2,000 employees including firefighters and traffic controllers participated in the walkout to demand a 6 percent pay increase or a minimum monthly raise of 250 euros.The work stoppage resulted in 445 canceled flight movements as terminals across the capital remained largely empty throughout the day.Airport management criticized the industrial action as disproportionate while scheduling the next round of wage negotiations for March 25.