Crises in the world’s most volatile regions could spell longer deployments and more uncertainty for fleet sailors.

The tense waters of Asia-Pacific or the Middle East could go for weeks or months without a U.S. aircraft carrier patrolling there this spring. But military planners are weighing whether this is the right moment to drop carrier presence, with strikes against Islamic State militants intensifying, rivalry between Saudi Arabia and Iran, and North Korea’s hydrogen bomb test. The other options are to cut one carrier’s needed maintenance short or extend a crew’s deployment beyond the 7-month goal — both unsavory options for fleet bosses.

At issue is a weeks-long period between when the Harry S. Truman Carrier Strike Group heads home from the Gulf in May and when the Dwight D. Eisenhower CSG deploys later that summer. That leaves the John C. Stennis CSG, which deploys in a few weeks, as the only flattop in either 5th or 7th Fleet. […]