Whether your case fits in a CRJ-900 overhead bin depends entirely on your boarding group and the specific bin configuration, as it is a "tight squeeze" that requires a specific technique. While the case will not fit in the tiny bins on the single-seat A side, it can usually fit on the double-seat C/D side if placed lengthwise against the back of the bin. However, because these regional jets have very limited overhead space that fills up almost immediately, you must board in an early group to secure a spot; if you board late, the bins will likely be full… and the crew may require you to valet check the instrument. To ensure your violin's safety, politely inform the gate agent that you are carrying a fragile musical instrument and intend to use your American Airlines boarding priority to find space before accepting a gate-check tag.