Start with the delivery need
Ask when the goods must actually be available, not only when they should depart. Include pickup, handling, customs and delivery in the planning window.
Compare the full cost
Freight is one part of the total. Handling charges, delivery scope, storage and the cost of unavailable stock may also affect the decision.
Check the cargo
Size, weight, packaging and special handling influence both feasibility and price. Restricted items require early disclosure and supporting information.
Sometimes, use both
A small urgent replenishment may move by air while the regular shipment moves by sea. Discuss the quantities and timing before selecting the plan.