A Tokyo court has upheld jail sentences for a US father-son duo who helped ex-Nissan chief Carlos Ghosn flee Japan, as the pair waived their right to appeal.

At their final hearing earlier this month, former special forces operative Michael Taylor was sentenced to two years in prison, and his son Peter to one year and eight months.

The men had admitted helping smuggle ex-auto tycoon Ghosn onto a private jet inside an audio equipment box in an audacious December 2019 escape.

"The verdict was fixed as of July 28" for the pair, a Tokyo District Court spokeswoman told AFP Thursday.

The Taylors and the prosecution both gave up their right to appeal within two weeks of the July 19 verdict, Kyodo News reported.

Ghosn, now an international fugitive in Lebanon, fled Japan with the Taylors' help while on bail following his shock 2018 arrest on financial misconduct allegations.

The Taylors arrived in Tokyo in March after losing a battle against extradition from the United States.

At their first hearing, in June, prosecutors described the almost-Hollywood details of the operation -- including that Ghosn was hidden in a large case with air holes drilled into it to slip past security at an airport.

A third man, identified as George Antoine Zayek, is also accused of involvement in the escape but remains at large.

According to the prosecution, the Ghosn family paid the Taylors more than $860,000 for preparation and logistical costs, and $500,000 in cryptocurrency for lawyers' fees.

Ghosn, who holds French, Lebanese and Brazilian passports, says he fled Japan because he did not believe he would receive a fair trial.

He has always denied the charges against him, arguing they were cooked up by Nissan executives who opposed his attempts to more closely integrate the firm with French partner Renault.