Jair I. Chavez enlisted in the Marine Corps on 27 October 2003. He attended recruit training at Marine Corps Recruit Depot (MCRD) San Diego. After graduating recruit training, he attended Marine Combat Training (MCT) at Camp Pendleton, California. Upon completion of MCT, he was reassigned to Naval Air Station Pensacola, Florida where he completed the Avionics Technician Intermediate level school.

In December 2004, Lance Corporal Chavez reported to Marine Aviation Logistics Squadron (MALS) 13 in Yuma, Arizona. In June 2005, he was promoted to Corporal and assumed the duties of avionics night crew shift supervisor in direct support of four AV-8B Harrier squadrons. In January 2006, he deployed to Iraq in support of Operation IRAQI FREEDOM 5-7.

In November 2006, he was promoted to the rank of Sergeant. As a Sergeant, he performed the duties as Work Center Supervisor, Collateral Duty Inspector (CDI), and Unit Color Sergeant. In February 2007, he deployed aboard the S.S. Curtiss for the Pacific Training Exercise 1-7, where he performed duties as the Avionics section CDI and supervisor for the exercise. In April 2008, he deployed on the U.S.S. Peleliu in support of the 15th Marine Expeditionary Unit (MEU).

Upon return from the 15th MEU, Sergeant Chavez received orders to MCRD San Diego for Drill Instructor School class 1-10. In December 2009, he was assigned to Company M, 3rd Recruit Training Battalion. He successfully completed eight recruit training cycles where he held the billets of Drill Instructor, Experienced Drill Instructor, and Senior Drill Instructor. In February 2011, he was promoted to the rank of Staff Sergeant.

After his successful tour as a Drill Instructor in January 2013, Staff Sergeant Chavez was assigned to MALS-13 in Yuma, Arizona. He performed duties as Work Center Staff Non-Commissioned Officer-in-Charge for the Electronic Counter Measure work center and Classified Material Control Chief. In January 2014, he was assigned as the Marine Aircraft Group 13 Avionics Quality Assurance Representative where he assisted in the development of the Naval Aviation programs for the F-35 Joint Strike Fighter.

In May 2016, Staff Sergeant Chavez was selected for the Assistant Marine Officer Instructor (AMOI) Program and was assigned to the Naval Academy Preparatory School in Newport, Rhode Island. In August 2016, he was promoted to the rank of Gunnery Sergeant. He served as the Battalion Drill Instructor, Operations Chief, and Marine liaison between the United States Naval Academy and the preparatory school. After completing his tour as an AMOI, Gunnery Sergeant Chavez was assigned to Marine Helicopter Squadron One (HMX-1), Quantico, Virginia.

Gunnery Sergeant Chavez reported for duty at HMX-1 in June 2019. He served in billets such as the MV-22B Avionics Intermediate Level Maintenance Chief, Aerial Observer, and Trip Leader for Presidential Support Detachments. In July 2020, he was promoted to the rank of First Sergeant and reported to The Basic School, Quantico, Virginia.

In July 2020, First Sergeant Chavez was assigned as the Company First Sergeant, Company F, Basic Officers Course 6-20, The Basic School. Upon the successful completion of the seven month course, First Sergeant Chavez was assigned as the Headquarters Company First Sergeant.

In May of 2022, First Sergeant Chavez was transferred to 3d Battalion, 1st Marine Regiment, 1st Marine Division, Camp Pendleton, CA, where he was assigned as Company First Sergeant for Company K and then Headquarters and Service Company. In April 2023, he deployed to Darwin, Australia as part of the Marine Rotational Force Darwin 23.3, Ground Combat Element.

In January 2024, he was promoted to his current rank and was assigned to Marine Light Attack Helicopter Squadron 169, Camp Pendleton, California.

Sergeant Major Chavez's personal awards include: Meritorious Service Medal, Navy Marine Corps Commendation Medal with two gold stars in lieu of third award, and Navy Marine Corps Achievement Medal with two gold stars in lieu of third award.