Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Type 1000
Communication Breakdown; Situational Awareness
Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Air Traffic Control Issued Advisory / Alert
Environment - Non Weather Related; Human Factors
The Captain started taxiing before we had clearance to do so. There were many other Company aircraft requesting taxi and push clearance. I knew he shouldn't have been taxiing; but didn't respond quick enough to question; to stop him; before Ramp Control asked what we were doing.
Getting ready to taxi to Runway XX from Gate YY in ZZZ. Several aircraft were pushing and getting ready to taxi at the same time; the radios were congested. Captain thought my FO had called for taxi clearance; and that Ramp had cleared us to taxi to follow an aircraft on the right that was passing behind. Captain initiated a turn and was called by Ramp that we had not been issued a taxi clearance. We were subsequently cleared to taxi and the rest of the flight was uneventful.I will listen more carefully to clearances in the future. As a general note; with the greatly reduced flying due to COVID-19; this was my first trip (second day) in over a month. Long layoffs and infrequent flying are causing my proficiency to be lower than normal and little things are occasionally slipping through the cracks. I am sure that I am not the only one.
Air carrier flight crew reported they began taxiing out without clearance. Captain stated lack of flying was a contributing factor.