Australian citizen Meke Fifita, 19, appeared at Manukau District Court on Thursday charged with breaching the Civil Aviation Act.
He provided information to another person relating to the safety of an aircraft, knowing the information to be false, police said.
The charge was laid after emergency services scrambled to Auckland International Airport on Wednesday night due to a "threatening comment" made while the Air New Zealand A320 was taxiing to the runway.
Fifita was arrested after the plane – bound for Sydney – returned to the gate.
The court heard Fifita was travelling on his own back to Sydney from Tonga, transiting at Auckland.
He typed "I have a bomb" because "I thought it was funny", the court heard.
When airline staff announced there had been a security breach, he knew "immediately" that it was because of his comment.
Fifita's lawyer, Jane Northwood, labelled the incident as the "grossly stupid event of the century" but said her client was distressed about what he had done.
"I've never met anyone more distressed or remorseful and overwhelmed," she said.
She arranged for an immediate sentencing because she was "gravely concerned" for his safety being remanded in Mt Eden prison, with no family support in New Zealand.
As an Australian citizen, Fifita faced either imprisonment or a fine.
Judge Anna Johns said she could not enforce a fine, but would consider an immediate reparation sum.
"Anyone with half a brain would understand that this is not a funny thing to do, given the times we live in," she said in court on Thursday.
Judge Johns said Fifita's actions came at a huge cost to the taxpayer, emergency services and Auckland Airport.
The estimated cost could be in the tens of thousands.
A reparation sum of $3000 was paid by Fifita's father in Sydney.