If hiring and growth continues I'd wager less than six months. Long term problem is that ORD is stagnant and increasingly senior so even when you get there the quality of life will only improve slowly. The wildcards are the Coronavirus and MAX grounding. If the economy goes into reverse after you make it onto the property, you might end up waiting upwards of a couple of years. Frankly, right now I'd be surprised if we don't enter a recession within the next 12 months. Too many red flags out there. Get your app in ASAP. As for aircraft, 737 is probably the better bet due to sheer fleet size.