The Hawaii Air National Guard has been conducting a big fighter jet preparedness exercise that even before the Jan. 13 nuclear missile scare had been rattling nerves because of heightened North Korea tensions.

The exercise, called Sentry Aloha 18-1, involves over 900 personnel and nearly 40 aircraft from Hawaii and five other states. Its goal is to provide Hawaii’s 154th Wing and California Air National Guard’s 144th Fighter Wing “realistic air-to-air combat training” for defensive and combat operations, the Air Force said.

Typically held at least twice a year in Hawaii, the exercise started Jan. 10 and will run to Wednesday, with two dozen aircraft including F-22 Raptors, F-15 Eagles, and F-16 Fighting Falcons taking off twice a day from Daniel K. Inouye International Airport.

Hawaii National Guard spokesman Lt. Col. Chuck Anthony said “there’s no connection to a North Korea-type scenario.” But across the U.S. military, forces are stepping up training and readiness should they be called upon for a North Korean conflict.

A jet fighter sonic boom Jan. 11 loud enough to rattle windows scared some residents of Kauai. The “boom” is caused when a jet flies faster than the speed of sound.

Kalani Walther, a chiropractor on Kauai, wrote on Facebook that, “Maybe it’s just me, but what with North Korea/Trump saber rattling, very loud explosions are particularly upsetting these days.”

Monique Rowan, who lives in Lihue, noted the aircrafts’ “loud sounds.”

“I’m sure many people found these sounds alarming, and not very many people seemed to know about it,” Rowan wrote.

The Hawaii Air Guard said on Facebook that the sonic boom occurred during fighter aircraft training in airspace north of Oahu.

“This training is necessary to ensure the readiness of our pilots who protect Hawaii 24/7. Although this type of training takes place on a regular basis, the sound of a sonic boom reaching land is rare,” the Air Guard said.

Anthony said sonic booms occur all the time.

“These are high-performance fighters and they fly supersonic every single time they train,” he said.

The Air Guard apologized to anyone who was upset and said it would review training procedures to minimize the impact to Hawaii residents.

Preparedness steps

Units from Alaska, California, Iowa, Oklahoma and Texas also are participating. F-16s from the Air Force’s 18th Aggressor Squadron out of Eielson Air Force Base in Alaska are sometimes part of the “red” enemy force, but also can be part of the “blue” home force. E-3 Sentry airborne warning and control system (AWACS) and tanker aircraft also are part of the exercise.

The fighter exercise comes amid a series of ongoing military preparedness steps being taken in the Asia-Pacific region.

The San Diego-based aircraft carrier USS Carl Vinson was visible off Waikiki Thursday morning as it headed to the western Pacific. The Vinson, which returned to San Diego in June from a deployment, will be filling in for the Yokosuka, Japan-based carrier USS Ronald Reagan while it undergoes a couple months of maintenance, U.S. Naval Institute News reported.

The Pearl Harbor destroyer USS Michael Murphy left with about 320 sailors Monday to join the Carl Vinson Strike Group.

Pacific Air Forces at Joint Base Pearl Harbor-Hickam recently announced nuclear-capable B-52 and B-2 stealth bomber deployments to Guam.

Six B-52H Stratofortress bombers and about 300 airmen from Barksdale Air Force Base in Louisiana deployed to Andersen Air Force Base in Guam as part of U.S. Pacific Command’s “continuous bomber presence” mission.

The B-52s are taking over at the end of the month for B-1B Lancers that trained with Japan and South Korea air forces on missions near or on the Korean Peninsula that infuriated North Korea. Pacific Air Forces said the B-52s “can carry nuclear or precision guided conventional ordnance,” and that the forward-deployed presence “demonstrates the U.S. continued commitment to allies and partners in the Indo-Pacific region.”

The Air Force also said three B-2 Spirit stealth bombers from Whiteman Air Force Base in Missouri also deployed with about 200 airmen to Guam.

“U.S. Strategic Command bombers regularly rotate through the Indo-Pacific region to conduct U.S. PACOM-led air operations, providing leaders with deterrent options to maintain regional stability,” Pacific Air Forces said.