What if a shipping delay causes me to breach my own customer contract?

Your position here involves two separate but connected relationships: first, your potential claim against the shipping company or carrier responsible for the delay, which would depend on the specific terms of your contract with them and whether the delay falls within circumstances they're contractually liable for, or whether it falls under an exemption for matters outside their reasonable control, and second, separately, your own potential liability to your customer for the resulting breach of your contract with them, which would depend on the specific terms of that separate contract, including whether it contains any force majeure or similar provision that might excuse your own non-performance given the underlying delay was outside your control. If your contract with your customer includes appropriate force majeure or similar provisions covering delays caused by circumstances genuinely outside your reasonable control, such as a significant shipping delay attributable to your carrier, this could potentially provide you with a defence or excuse for your own delayed performance, though whether this actually applies depends entirely on the specific wording of your particular contract with your customer, meaning generic assumptions about being automatically excused simply because the underlying cause was a third party's delay would not be safe without checking your actual contract terms. Given the genuine complexity of navigating both your claim against the carrier and your potential exposure to your own customer, it would be worth consulting a lawyer to properly review both sets of contracts and advise on your best approach to managing both relationships.