If you really want to aim for an airline, and many feel it is a worthy goal even if they do not make it a career, make sure you accrue enough flight time towards meeting ATP minimums by the time you want to apply. See FAR 61 Subpart G for the specific numbers. You can arrive at 1500 but still not have what you need for ATP minimums if you do not plan for it a bit. To get what you need, CFI work is helpful. Multiengine time used to be big, numbers like 500 were common, but that requirement has fallen by the wayside recently so do not do a ton of multi. 100 hours of quality flying toward the end of the 1500 would be great.