There is suspicion the planes may be changed or loaded in smaller airstrips

In an investigation that has major repercussions on aviation safety, the Enforcement Directorate is probing whether chartered planes were used to ferry truckloads of cash in and outside the country.

The probe, which involves multiple agencies, is at a formative stage, but has found at least a few instances whereby chartered planes used by VIPs were modified with cubbyholes where cash could be stashed and carried undetected.

Investigators have, however, told NDTV there is no evidence yet of the owners of such chartered planes or their VIP clients being involved.

The issue came to light in May when the Central Bureau of Investigation or CBI arrested a former journalist and businessman, Upendra Rai, for obtaining an aerodrome entry pass from the Bureau of Civil Aviation Security by giving fake credentials.

The pass gave him access to all airports across the country. Though the CBI arrested the businessman, executives of private plane operator Air One and some airport officials, the investigators did not reveal Mr Rai's motives for getting such an all-access pass.

The modus operandi was the criminals chose chartered planes being used by VIPs which would have minimum amount of security checks

This week, the Enforcement Directorate or ED revealed that they have seized all his assets worth more than Rs 26 crore, including flats in south Delhi's posh Greater Kailash and Connaught Place.

The ED also revealed that he would extort companies and channel funds through shell companies.

NDTV has, however, learnt that investigators suspect he was working with an aviation engineer to create invisible pockets in planes. These then would be stashed with illicit cash without the knowledge of the owners or the client who was flying the plane.

The modus operandi, according to people with direct knowledge of the matter, was that they were targeting chartered planes being used by VIPs which would have minimum amount of security checks.

Investigators have also confirmed that Air One, which Mr Rai was associated with, had parked its planes for long periods of time in Dubai. They also found it suspicious that the air operator used Al Maktoum International Airport in Jebel Ali, some 37 km south-west of Dubai, which has less scrutiny than the main Dubai airport. Apart from the Dubai visits, Air One planes frequently went to Russia.

"He was doing a lot of work for officers," said a senior ED officer about Upendra Rai.

The Enforcement Directorate has seized assets worth over Rs 26 crore of a businessman involved in ferrying illegal cash in chartered planes

However, when asked specifically about the probe, he said that the agency was still collecting information and evidence. When NDTV asked the CBI, they said they were collecting more information about his cash transactions, but said they were unaware of this particular ploy.

Investigators are now tracing suspicious activities after demonetisation in November 2016. Just after the notes ban was announced, Delhi International Airport Ltd or DIAL received queries from a foreign agency about an internationally registered plane that was caught ferrying large amount of cash from the national capital. The airport authorities, however, declined to give details of what was found in that probe.

There is suspicion that the planes may be changed or loaded in smaller airstrips in places like Haryana's Hissar. There are 400 airstrips across the country, and only 100 are used commercially.

However, even if private planes are to be loaded in those airstrips, they have to clear customs and that's where having a VIP on board helps.

It is unclear who is responsible for the alleged security breach that has been taking place on such planes. BCAS, which gave Upendra Rai the pass, told NDTV that it wasn't just their responsibility, but "issued on the basis of application made by the person duly endorsed by his employer such as Air One and further endorsed by Airport operation in this case DIAL."