Really? I have been flying with guitars for decades and the very large majority of the time I get the guitar on, period. I will reiterate my suggestions:
1. Ask no questions
2. Keep guitar out of sight of airline personnel while you wait
3. Just show your boarding pass and walk on to the plane keeping guitar upright alongside you and hope they don't notice.
4. If asked to gate check, accept the ticket and then try and get it on anyhow, but accept the gate check, its never been an issue for me
5. Above all, don't be late and smile/be nice, just the way your Mom taught you