This paper examines the impact of resource availability, namely labor and flight equipment availability, on entry into the US airline industry. The general thesis is that when labor and/or flight equipment is in scarce supply, the cost of starting and operating a new airline, or the cost of expanding onto new routes, is high. The paper found a positive correlation between new aircraft delivery and new entry onto routes by majors but a negative correlation between new aircraft delivery and entry onto routes by non-majors. The paper also found a negative correlation between major carrier salary levels and entry by majors but a positive correlation between major carrier salary levels and entry by non-majors.