Shell Oil is one step closer to drilling offshore from Alaska's northern coasts this summer.
The Environmental Protection Agency's appeals board on Friday denied petitions to review the air permit for its drilling ship Kulluk.
Federal authorities earlier denied review petitions for Shell's other ship, the Noble Discoverer. Environmental and Alaska Native groups have appealed the Discoverer's permits in federal court. Shell spokesman Curtis Smith says he expects the Kulluk's permit also to be challenged but both to survive.
Earthjustice, an environmental law firm representing the groups, didn't immediately return a message Friday.
The Discoverer has been granted permits to drill in both the Beaufort and Chukchi seas; the Kulluk is limited to the Beaufort.
Shell still needs three additional approvals before it can begin drilling this summer.