Scales to Play Over F#maj9
Every chord is a subset of several scales: any scale that contains all of a chord's tones fits over it. Pick a chord to see the matching scales from its own root, the major keys the chord belongs to, and full fretboard diagrams for every scale on guitar.
A F#maj9 chord contains the notes F# – G# – A# – C# – F. Any scale that includes every one of those 5 tones fits over it — from the root F#, that means F# Major, F# Lydian and F# Mixolydian Bebop. Start with the first scale listed: it is the most common choice, and the others color the same chord tones differently.
F#maj9 is also diatonic to 2 major keys: C# major (relative minor A#m), F# major (relative minor D#m). In a song from one of those keys you can also solo with the key's own major scale or its relative minor pentatonic across the whole progression, not just this chord.