Small Transport
Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 64; Flight Crew Total 2005; Flight Crew Type 515
Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Human Factors
On final approach to Runway 13 into MDT; we were cleared to intercept the visual final approach course. Due to the haze and unfamiliarity on the airports on separate sides of the river; we mistook CXY Runway 12 for MDT Runway 13. We had the GPS 13 approach loaded for reference due to the ILS 13 being out; but prior to turning inbound on the final we were given a vector for the intercept final approach course. I mistook the Capital City airport (CXY) Runway 12 for MDTs Runway 13. We were asked if we had MDT in sight; thinking we did; and cleared for a visual approach; I made a descent for CXY Runway 12; still not realizing it was not MDT Runway 13. MDT Tower asked then told us we were aligned with CXY and gave a low altitude warning. I immediately added power and climbed. I then aligned with Runway 13 at MDT and landed.
We were approaching Harrisburg Int'l from the west when we were instructed to intercept the final course for a visual approach to RWY 13. It was hazy with visibility low enough that the only airport in sight was Capital City (CXY).  Its RWY 12 is oriented similarly to RW 13 at MDT; so when we were asked if we had the airport in sight; we said we did.  The airport was closer by a few miles than our FMS was indicating so we configured for landing and steepened the approach. MDT Tower then asked if we could be approaching Capital City as we were lower than we should've been. At that point; MDT was also visible. The pilot flying applied power and climbed enough to conduct a normal approach to RWY 13.The haze contributed; as did the vector for a visual.  Interestingly; the proximity of these two airports is compounded by the fact that the airport on the south side of the river (CXY) is actually north of MDT; which is on the north side of the river due to bends in the river.We could've avoided the error if we'd been more familiar with the area and/or declined the visual approach.
Corporate jet flight crew reported receiving a low altitude warning from MDT Tower when they began their descent for CXY; a nearby airport.