The Fortescue Ltd (ASX: FMG) share price is falling on Tuesday.

In morning trade, the iron ore giant's shares are down 2% to $24.13.

This follows the release of the miner's third-quarter update.

For the three months ended 31 March, Fortescue reported iron ore shipments of 43.3Mt. This was down 6% on the prior corresponding period and fell short of the consensus estimate of 44.8Mt.

Management blamed the miss on the impact of an ore car derailment on 30 December and weather disruptions.

Things would have been significantly worse had the company not delivered a record month in March. During the month, the company achieved shipments of 18.7Mt. This means that approximately 43% of its quarterly shipments occurred during March.

In light of its lower shipments, Fortescue's Pilbara Hematite C1 cost came in at US$18.93 per wet metric tonne (wmt). This was 7% higher than during the second quarter of FY 2024.

Another disappointment was the average revenue per dry metric tonne (dmt) that Fortescue received. It recorded an average of US$104 per dmt, which represents 85% of the average Platts 62% CFR Index for the period. Management advised that revenue realisation was affected by the timing of sales during the quarter.

Analysts at Goldman Sachs were forecasting an average price of US$109 a tonne and an 88% revenue realisation.

At the end of the period, the company had a cash balance of US$4.1 billion and net debt of US$1.2 billion.

The good news for shareholders is that the company has reaffirmed its shipments and cost guidance despite the above.

FY 2024 total shipments are expected to be 192Mt to 197Mt. Though, shipments are now expected to be at the lower end of the range due to the aforementioned derailment and weather impacts.

In addition, the company's Pilbara Hematite C1 cost guidance remains between US$18.00 to US$19.00 per wmt for the 12 months.

One item that has been reduced is the company's spending on its Fortescue Energy net operating expenditure. This has been reduced by US$100 million to a total of US$700 million thanks to cost-saving initiatives.

Fortescue's chief executive officer, Dino Otranto, said:

The Fortescue team pulled together to successfully implement our recovery plan, and we had a record month for shipments in March of 18.7Mt contributing to 43.3Mt for the quarter. We also set a new record for railed tonnes, all while continuing to improve our safety performance.

Our decarbonisation plan is progressing well, with our first operational electric excavator moving over one million tonnes of material since being commissioned. Our battery electric haul truck prototype has completed its first phase of testing, exceeding the performance expectations of the battery power system.

The Fortescue share price remains up more than 15% over the last 12 months.