ISAL (an acronym for International Surface Air Lift) is an international bulk mailing service offered by the U.S. Postal Service (USPS).
ISAL was begun in the 1970’s. The publisher McGraw-Hill was highly instrumental in helping bring about ISAL service. McGraw-Hill was interested in finding a way to reduce the time it took for publishers periodicals to be delivered to their destinations via surface mail. McGraw-Hill proposed that the USPS airlift surface mail to its destination, rather than send it by sea. The result was a hybrid “air/surface” delivery system that was called ISAL.
Early ISAL service did not fly directly from the United States to every country of destination; most mail destined to Europe, for example, was flown to Brussels and sent onward from there, sometimes via truck or rail.
Few mailers could take advantage of ISAL when it was first introduced, as the USPS imposed strict minimum shipment size requirements. In the 1980’s, an industry emerged with companies that offered an “ISAL consolidation” service. This led the way for smaller mailers to use the service; the consolidators charged a premium over the USPS rates.
Today, ISAL is a popular international bulk mailing service. Other postal administrations offer international mailing services that compete with ISAL. Some of these, including other mailing methods such as direct-entry, are less expensive than ISAL.