B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 293; Flight Crew Type 35
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Rejected Takeoff
Aircraft; Human Factors
First Officer's leg.  Departing at approximately 60 knots the First Officer's window slid open.  I announced and took control of the aircraft.  The First Officer was unable to secure the window and I initiated the abort at approximately 90 knots.  The surprising nature of a window opening and the noise involved with an open window during takeoff led to the delayed abort decision.  I believe the transition training for new B737 pilots needs to address aircraft differences with more detail.
Cleared for takeoff and at approximately 60 knots my (RH) cockpit sliding window slid open. As I was the pilot flying; the Captain immediately announced; 'I have the aircraft.' I initially made an attempt to close and re-secure the window; but due to my lack of experience with the 737 window latching mechanism; as well as the element of surprise; I announced; 'I can't get it.' The Captain immediately initiated the reject; communicated with Tower; and exited the runway. We taxied clear of the active taxiway; determined the cause of the event; re-secured the window; and determined the brake cooling consideration. The Captain communicated with our Dispatch and Maintenance offices; a logbook entry was made; and we continued the flight to our destination without incident.I believe had I been more thorough with preflighting the cockpit window and confirming it to be fully latched and secured; this event would not have occurred. Also; having transitioned from a different type of aircraft at my previous carrier; I confused the sliding window latching mechanism with that of the other aircraft. In the future; I will be diligent to thoroughly preflight the cockpit sliding window; which is the last but definitely not the least important item on the First Officer flight deck preparation flow.
B737 flight crew reports a rejected takeoff at 90 knots when the First Officer's sliding window opens at 60 knots during takeoff.