This achievement is a pain. I finally came back to it in FX3 after years of annoyance in FX2. Here's a quick overview of how I finally managed to unlock it.
* Obtain 100+ "commendations" (money)
* Upgrade your starfighter shields three times
* Start Lone Fighter mode (rewind works in Lone Fighter mode)
Before today I probably played Lone Fighter mode over 100 times. So frustrating. I read the guide for this achievement in Pinball FX 2 and the author said not to worry about upgrading your shields because it takes too long and he wasn't sure why sometimes upgrades were available to buy and sometimes they weren't. I decided to crack the mystery.
One detail I borrowed from the Pinball FX 2 guide for this achievement:
* Choose the Empire. It definitely feels easier to shoot down XWings than Tie Fighters.
OBTAIN 100+ COMMENDATIONS
Commendations are like money. You need them to buy upgrades in the store. You get them by completing objectives, missions, etc. If you don't have at least 10 commendations when you light UPGRADE and try to go to the store, you won't have the option to buy anything (you'll just get a score boost instead).
These came naturally to me after completing Mission 1, part of Mission 2 and handful of the shot modes (Evade, Repair, Supply, etc.).
UPGRADE YOUR STARFIGHTER SHIELDS THREE TIMES
To upgrade your shields, shoot the right orbit seven times to light UPGRADE, then shoot the ramp under the green crosshairs. If you have at least 10 commendations you will go to the "shop" where you can select Starfighter Shields. Shield upgrades cost the following:
* 1st Upgrade - 10 commendations
* 2nd Upgrade - 30 commendations
* 3rd Upgrade - 60 commendations
* 4th Upgrade - ??? (I suspect 120 but never went back with enough commendations)
You can only buy one upgrade per visit to the store so you'll need to go through the steps of lighting UPGRADE and visiting the store three times. It is time consuming but I believe it helps your chances of completing Lone Fighter mode immensely. Especially considering the UPGRADE lane is one of the easier shots on the table.
START LONE FIGHTER MODE
To start Lone Fighter mode you need to:
* Hit the three targets in the center of the table.
* Hit the squad hole in the lower right of the table.
The three targets are a pain to hit. I couldn't figure out an easy way to consistently hit them. Once you light one, the lit targets will cycle every time the left or right bumpers are hit. When all three are lit, the squad hole will light. It's pretty easy to hit by hitting the ball off the very end of the left flipper.
Normally you start Lone Fighter mode with seven shields. For each shield upgrade you purchased you will get an additional shield. If you bought three, you'll start the mode with 10. I failed the mode a few times after buying two shield upgrades and completed it the first time I attempted it after buying three shield upgrades.
Your shield upgrades stick with you for the duration of the entire game so if you don't get it your first time through Lone Fighter mode, you can just light the three targets and try again.
P.S. Don't forget that rewind works in Lone Fighter mode. If you miss a few ships in a wave you can hit rewind to try to get them again.