SA National Defence Force spokesman Siphiwe Dlamini could not immediately confirm whether the department had received the notice.
Sandu said it had served the department with the document.
“I can confirm that the notice has been served on the department this afternoon,” said secretary for the SA National Defence Union, Pikkie Greef on Monday.
The union gave the defence force 30 days to say whether it intended going ahead with charges against Lt-Col Christine Anderson and Lt-Col Stephanus van Zyl or whether they would drop the matter.
“If there is no response, we will go to the High Court to force them to act,” said Greef.
A chartered commercial aircraft from India, ferrying more than 200 guests for the wedding of Vega Gupta, whose family has business interests in South Africa, and Aakash Jahajgarhia, landed at the Waterkloof Air Force base in April last year.
The landing sparked widespread criticism and several investigations were launched. A government investigation exonerated President Jacob Zuma and his ministers, and found the landing was the result of “collusion by officials”.
The two officials were implicated in the incident.
In October, they were handed a preliminary charge sheet indicating that they disobeyed a written order.
The pair are currently on paid suspension.