Air carrier captain reported an aircraft turning in front of their aircraft on final into mdw. Pilot...

Narrative:

We were cleared ILS 4R approach; 170 knots till citgo. Aircraft joined final ahead of us close; from the north; which is unusual. They checked-in with tower 'back with you.' I saw us closing on this traffic ahead on final and started slowing prior to citgo; at the same time tower called '(call sign)'; we responded; then tower called again as if they didn't hear our reply. We were instructed to go around and turn left; we complied. Vectors back around for another ILS; complying with ATC assigned speed; re-cleared approach behind [another aircraft]. Tower told us to slow to final due to traffic ahead; we were already fully configured and decelerating through 10 knots above target speed. We landed on 4R. Along with our taxi instructions we were instructed to call approach control for a possible pilot deviation. I called [the] manager air traffic systems; and he called on our behalf.we complied with all ATC instructions; and I believe ATC did not provide proper spacing; or the other aircraft did not comply on our first approach attempt. The second approach; ATC was again concerned with spacing.

Original NASA ASRS Text

Title: Air carrier Captain reported an aircraft turning in front of their aircraft on final into MDW. Pilot was then called by ATC and told to go around. Vectored back to final and landed without incident. Crew was advised to call ATC for possible pilot deviation.

Narrative: We were cleared ILS 4R Approach; 170 knots till CITGO. Aircraft joined final ahead of us close; from the north; which is unusual. They checked-in with Tower 'back with you.' I saw us closing on this traffic ahead on final and started slowing prior to CITGO; at the same time Tower called '(Call sign)'; we responded; then Tower called again as if they didn't hear our reply. We were instructed to go around and turn left; we complied. Vectors back around for another ILS; complying with ATC assigned speed; re-cleared approach behind [another aircraft]. Tower told us to slow to final due to traffic ahead; we were already fully configured and decelerating through 10 knots above target speed. We landed on 4R. Along with our taxi instructions we were instructed to call Approach Control for a possible Pilot Deviation. I called [the] Manager Air Traffic Systems; and he called on our behalf.We complied with all ATC instructions; and I believe ATC did not provide proper spacing; or the other aircraft did not comply on our first approach attempt. The second approach; ATC was again concerned with spacing.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1413993
Time
Date	201701
Local Time Of Day	1201-1800
Place
Locale Reference	MDW.Airport
State Reference	IL
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 204 Flight Crew Type 12796
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Clearance

Air carrier captain reported an aircraft turning in front of their aircraft on final into mdw. Pilot was then called by ATC and told to go around. Vectored back to final and landed without incident. Crew was advised to call ATC for possible pilot deviation.