Karachi Airport and RAF Drigh Road

[Petrusja]

RAF Drigh Road was an airfield south of the road of that name outside Karachi. Early airliners used 'Drigh Road Airport', likely the same location.

But by 1945 there was a separate airfield, 'Karachi Airport', with two runways, to the north of Drigh Road and the railway line:

http://www.rafcommands.com/galleries...DrighRoadFront

That airport became the current Karachi - Jinnah International (OPKC / KHI), and Drigh Road became PAF Faisal.

My question is, when was the northern airfield/airport built?

GlobalSecurity.org mentions:

The institution of the Empire air mail scheme meant that in India, as elsewhere, very serious attention was paid to the work of providing adequate ground facilities both for trunk and feeder services. One addition to the number of works being and to be carried out by the Civil Aviation Directorate in India was the new administrative building at the Drigh Road Airport of Karachi. This was formally opened, on 05 December 1938.

So was the northern airfield begun later, during the war? Or was the northern side also called Drigh Road, and was it there maybe even before the opening of the administrative building in 1938?

In other words, which field was used by Tata Airlines, Imperial Airways and KLM in the 1930s?

Thanks, Peter