So tight is the tanker market, oil traders are reportedly booking Jones Act ships to meet the demand.

Reuters reported on Monday that traders have started to book the US-flag vessels — required by law to be primarily owned, crewed and built by Americans, and generally used only in domestic trades — for floating storage and international voyages.

Tanker rates have skyrocketed since early March, when a breakdown in talks between Opec and allies broke down, leading Saudi Arabia to begin increasing oil production in the face of widespread demand destruction brought on...