What is the difference between ETA and ATA?

Estimated Time of Arrival (ETA) is the carrier's projected date and time for vessel arrival, recalculated as weather, vessel speed, and port congestion at prior calls change during transit, while Actual Time of Arrival (ATA) is the confirmed time the vessel actually berths and becomes fixed once it occurs. Independent dispatch data indicates that ETAs published more than 5 days before arrival at Los Angeles/Long Beach show an average variance of 1-2 days versus ATA, while ETAs updated within 48 hours of arrival are typically accurate within a few hours as the vessel's approach reduces remaining variables.

ETA vs. ATA: Understanding Vessel Arrival Tracking

Cost structure / standard tiers

ETA accuracy doesn't carry a direct fee, but planning around inaccurate ETAs creates downstream costs through missed appointments and idle resources.

ETA Lead Time	Typical Variance vs. ATA	Planning Impact
7+ days out	±1-2 days	Use for general capacity planning only
3-5 days out	±12-24 hours	Reasonable for booking drayage appointments
24-48 hours out	±2-6 hours	Reliable for warehouse labor scheduling
Berth-confirmed (ATA imminent)	Near-zero	Final confirmation for same-day operations
Missed appointment due to ETA-based booking	N/A	$50-150 rebooking fee (terminal/drayage dependent)

Free time for demurrage purposes is calculated from actual discharge (following ATA and berthing), not from the originally published ETA, so vessel delays push the entire free-time clock back accordingly.

Risk mitigation / operational guidance

Avoid booking drayage appointments or warehouse labor based on ETAs published more than 3-5 days out — use that window for capacity planning only, and confirm closer to arrival before committing resources. Track milestones beyond ETA/ATA, including "vessel berthed," "discharge complete," and "available for pickup" or "customs released," since each can lag actual arrival by hours to days depending on terminal workload. Subscribe to carrier EDI/API feeds or third-party visibility platforms that refresh status as the vessel approaches port, since accuracy improves substantially inside the 48-hour window. Build a standard buffer (e.g., book appointments for the day after the most recent ETA update) for time-sensitive cargo where a missed appointment carries rebooking costs.