This is correct. The day you start at the Academy is Day 1, also known as your Service Computation Date (SCD). This date sets all your seniority, retirement dates, vesting, etc. It will stay with you through any and all Federal jobs you may hold, not just the FAA. You'll be on probationary status for a year meaning you can be terminated without "cause".
Also, in regards to the TSP, you may start contributing from day 1 (you will receive an automatic 1% contribution from the agency whether you contribute or not). The agency automatic 1% and any other matching up to 5% is subject to revocation until you are "vested" which is on the 3rd anniversary of your SCD. In other words if one resigns or is terminated before vesting, the gov't takes their TSP money back! Most people do at least a 5% contribution to obtain the maximum 5% matching funds from the gov't.
If you join the TSP your contributions will all go into the Traditional TSP G fund until you change it. The G fund is stable but very little growth, so get with an advisor to assess risk and choose the right funds. Most people at least use the Lifecycle Funds but one can do better with individual funds if they know what they're doing and have a tolerance for risk. The Traditional TSP uses your pre-tax or "tax deferred" dollars to fund it, and the Roth TSP uses after tax dollars to build the account. When you retire you either pay taxes on the traditional version or pay zero taxes on the Roth version. All gov't contributions and matches go into Traditional though. Get your tsp.gov password ASAP and manage your funds! All the data tells us that early and steady investment into retirement accounts (with funds that have a good return) is what makes millionaires and generational wealth.
Sign up for the FEGLI group life insurance day 1 and max out all the categories you can. They have open season VERY rarely...the last 3 were 1999, 2004, and 2016! If you have qualifying life events and are already enrolled you can make changes but it's good to get in on the ground floor. I have everything maxed out and with a wife and kids it's around $600K in coverage for about $35 per paycheck, When one reaches 45 years old though, the benefits start to reduce and the premiums start to become cost prohibitive compared to buying private term life insurance. Before that though, it's a great deal.
If you want to know anything else, just ask. I really like to help people with this type of information.