Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Fatigue; Distraction
Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Other / Unknown
Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors
Approach gave us a heading to intercept the 28C localizer.  Captain turned to that heading but didn't not select a different NAV mode.  I assumed he was waiting for wings level to select NAV.  At wings level; he did nothing so I asked if we were cleared for the approach.  He thanked me and selected NAV.  At that point I believe we were too far to intercept the course.  Approach asked if we were going through course.  They gave us a heading to the south to reintercept.  Captain left autopilot on and the aircraft was slow turning and I didn't take the plane and turn the autopilot off.  Approach called traffic 1;000 ft above on the 27L approach.  We had the traffic and were given an additional turn south; and decent to 4;000 ft and recleared for the Visual for 28C. [Reporter stated a contributing] cause was end of a 4 day trip and we were tired.  Also; we had more discussion in sterile [cockpit] than normal as an aircraft ahead of us had reported a drone approximately 400 ft below them on final.  I was uncertain which aircraft this was relative to our position on the approach; so we were discussing that. [Reporter resolves to] pay closer attention.  Disengage autopilot to correct more quickly.
I was pilot flying.  We were vectored to the ILS for runway 28C in ORD. We were instructed to join localizer for 28C. I was planning to use LNAV  and VNAV until outside the final approach fix. As we turned to vector to join; I paused before hitting LNAV because usually the aircraft would turn towards course immediately and if you wait it will fly the heading and then join. Approach had us a little too close for that and with 15 knots of wind from south we flew through the course. The FO pointed that out and I turned at same time as approach gave us another heading to join. We were also given a lower altitude. Auto pilot was on. We then joined the localizer and continued the approach. We were vectored close in and with the 15 knot cross wind; pushed through localizer. I needed to do better monitoring of where the course was.
Air carrier First Officer reported approach clearance deviation resulting in ATC assigned vectors to restart the approach for an uneventful landing.