The U.S. Department of Transportation's Office of Aviation Consumer Protection is currently investigating Delta Air Lines as it cancels hundreds of flights for the fifth day after cybersecurity firm Crowdstrike installed a faulty software update that halted many airport systems.

Delta has canceled more than 5,500 flights since the outage began Friday morning.

Delta had canceled 415 flights as of Tuesday morning, which was more than any other airline, according to reports. As of 9am on Wednesday, Delta topped all airlines with 427 cancelled flights, according to FlightAware data.

CBS News confirmed that the Transportation Department is "investigating Delta Air Lines following continued widespread flight disruptions and reports of concerning customer service failures."