An FBI agent alleges in court documents that Roman Abramovich used a series of shell companies and trusts to purchase two luxury aircrafts for $400 million.

The FBI has linked the Russian billionaire to five shell companies located in Cyprus, Jersey, and the British Virgin Islands.

The documents filed in support of the US application for a seizure warrant shed light on the financial structures individuals have used to control their foreign assets. The wealthy can achieve a certain level of buyer anonymity if they layer shell companies, trusts, and holding companies in tax havens.

A flow chart showing the 5 shell companies the FBI alleges Roman Abramovich used to buy luxury jets. Alex Ford/Insider

Gary Kalman, executive director of the anti-corruption organization, told Insider that most countries don't require companies that sell luxury goods to follow anti-money-laundering procedures.

Kalman said that the only thing they have to look at is the purchaser. If it's five layers down, they were just looking at the trust trying to purchase the plane that didn't haveAbramovich's name on it.

He explained that creating multiple layers of shell companies to oversee assets worth millions of dollars is common among people of Abramovich's net worth. Setting up companies in different countries makes it harder to build a case due to the time it takes for law enforcement to cross borders.

Kalman said that it can be hard to track down if they do it correctly.