4K
B Tier
N16551 (United, readable on engine), N663CJ (Contour, partially readable on tail)
Contour Airlines (foreground), United Airlines (background)
CRJ1 (Bombardier CRJ-100/200), possibly CRJ-200 for Contour; B738 (Boeing 737-800) for United
ORD/KORD
Bombardier (Contour), Boeing (United) CRJ-200 (Contour), Boeing 737-800 (United)
Pushback at ORD.