The shipment is booked, the container is on its way – and suddenly the ETA (Estimated Time of Arrival) changes. For many companies, the immediate question is: "Why is our container arriving late?" The good news is that a delay does not automatically mean something is wrong with the goods or the container. International maritime transport involves many interconnected processes. Even minor changes can affect the entire schedule. In this article, we look at the most common causes of delays and explain which factors can be influenced – and which cannot.

Weather – safety first

Container ships are built for the open ocean. Nevertheless, extreme weather conditions can affect schedules. Storms, heavy seas, or typhoons often force ships to reduce speed or adjust their routes. The goal is to ensure the safety of the crew, the cargo, and the vessel. Such delays cannot be prevented by either the shipping line or the freight forwarder.

Congested ports

Many international container ports are operating at capacity. If several ships arrive at the same time or there is an increase in freight volume, waiting times can occur. The ship may have to wait for an available berth before unloading can begin. Delays can also occur after unloading – for example, during container availability or onward transport.

Transshipment – when the container is reloaded

Not every container travels to its destination port on a single ship. Often, a so-called transshipment takes place along the way. During this process, the container is transferred from one ship to another at an intermediate port. If the first ship is delayed or schedules change, the planned connection may be missed. In this case, the container is rebooked onto the next available ship, which extends the transit time.

Roll-over – when the container is shipped later

Another reason for delays is a so-called roll-over. This occurs when a booked container is not loaded onto the intended ship as planned, but is moved to a later departure. Reasons for this can include:

• Capacity bottlenecks
• delayed pre-carriage
• operational changes by the shipping line
• last-minute schedule adjustments

A roll-over does not mean the booking has been cancelled – the container is simply traveling on a later ship.

Customs inspections

In both the export and import countries, customs authorities may select a shipment for additional inspections. This does not necessarily mean the entire container has to be opened. Possible inspections include, for example:

• Document checks
• Scans
• Physical inspections
• Request for additional documentation

Depending on the type of inspection, the release of the shipment may be delayed accordingly.

Incomplete or incorrect documents

Careful documentation is one of the most important prerequisites for smooth transport. Missing or contradictory information can lead to queries before shipment or delay customs clearance in the destination country. Typical examples include:

• incomplete commercial invoices
• incorrect product descriptions
• incorrect HS codes
• missing proof of preference or origin (where required)

Many of these delays can be avoided through careful preparation.

Schedule changes

Shipping lines regularly adjust their schedules. Reasons for this include:

• changes to port rotation
• omission of individual port calls
• adjustments based on capacity utilization
• late arrival of the vessel from a previous voyage

These changes often affect the ETA of the entire transport chain.

Strikes and technical disruptions

External factors can also delay transport. These include, for example:

• Port strikes
• Work stoppages at terminal operators
• Technical disruptions at port facilities
• Defects in cranes or other handling equipment

Such events are usually impossible to foresee and can delay both loading and unloading.

Not every delay can be avoided

International supply chains involve numerous parties – from shipping lines and port operators to customs authorities and transport companies. Some potential delays are beyond the control of all parties involved. However, careful planning, complete documentation, and continuous monitoring of the transport process help to identify risks early and reduce avoidable delays.