a way of understanding

First, we know a couple of things about his age from canon:

We know from "Chimney Begins" that Tommy was not a probie in 2005 when Chim joined. So he'd been there at least a year before that. For the sake of making him as young as possible, we will say that he has ONLY been there a year. We also knew that he "learned to fly" in the army.

So, that means:

He had to have joined the LAFD ~2004.

Had to have completed the necessary requirements for army pilots prior to that. For Army pilots joining prior to October 1, 2020, there was a 6 year service requirement after completing flight school.

To be a pilot, Tommy also had to be either a Commissioned Officer OR a Warrant Officer. Assuming he was not an officer, that means he had to complete all of the following before he could becoming a pilot: Army Basic Training, Warrant Officer Candidate School (WOCS), and Army helicopter flight school.

To make Tommy AS YOUNG AS HUMANLY POSSIBLE IN THIS TIMELINE: We'll also assume he joined the army at 17 with parental permission, which you can do because the USA is stupid and because his father seems like the sort - and also because we are going to make Tommy as YOUNG as he can possibly be in 2026 to prove my point:

Age 17: Graduates High school, Enlists in Army and does Basic Combat Training ~ 2.5 months

Age 17: Warrant Officer Candidate School ~1.5 months

Ages: 17–18 Army helicopter flight school (IERW) ~12 months (Can be up to 18 months, but we are making this the shortest timeline possible)

Ages 18–24: Aviation service obligation 6 years

Age 24: Leaves Army (Here, we give Tommy a LOT of assumptive grace. Getting into the LAFD Academy is hard, but we'll assume his officers wrote nice things or whatever and he got in right away.)

Age 24 :LAFD Academy: 22 weeks

AGe 24: Starts Probie Year

Age 25: "Chimney Begins" - has been with LAFD for at least a year. (in 2005)

SO, if he's 25 in 2005, that would make him born in 1980. In 2026, that that makes him no younger than 46. If he's born in 1980, that means he is 11 years older than Buck's 1991 birth year, which is fun and sexy if you aren't boring (and they are not.)

Notes:

Now, in truth, in a realistic timeline, Tommy would be older still.

He'd spent closer to 18 months in flight school and he probably had to take some time to apply/wait/join the LAFD academy, and maybe his parents weren't dicks and made him wait to 18 before he signed his life away to the military and/or maybe he gradated at the age of 18.

There's also issues with waiting for admission to WOCs and flight school.

And we have no IDEA how long he was in the LAFD before Chim came along

Honestly, 48 is more realistic and he could easily be celebrating his 50th birthday OR BEYOND. IF YOU AREN'T A COWARD.

BUT~ if you want him as young as possible, 46 is the bottom floor of what can be going on here in 2026. He can definitely be older, but he can't be younger and have the timeline make any sense.

In conclusion:

Sources:

(Just sources; don't join the military, kids.)

Army Aviation Special and Incentive Pay Policies to Promote Performance, Manage Talent, and Sustain Retention

LAFD requirements recruitment video

Rotary Wing Aviator Warrant Officer 153A