"At least 42 militants of Lashkar-e-Islam were killed and two militant hideouts were also destroyed," Shafeerullah Wazir, the Khyber administration chief, said.
"The death toll may rise as dozens of others were also injured in the airstrike."
Death toll confirmed
A military official confirmed that the incident had taken place and the death toll was correct.
"The air strike was launched on a tip-off that a meeting of the Lashkar-e-Islam group was going on in Tirah," the official told the Agence France Presse news service.
The area where the attack took place adjoins the northwestern city of Peshawar, scene of a series of bomb attacks blamed on the Taliban in recent months and increasingly viewed as a seat of instability in Pakistan.
"There was an attack by a fixed-wing aircraft," Kamal Hyder, Al Jazeera's correspondent in Pakistan, said quoting witnesses.
"A jirga [tribal meeting] was hit. After that nearby residents came to pull people out of the rubble. Then a second and, maybe, even a third wave of attacks hit them."
The violence came as a Pakistani military offensive against Taliban-allied fighters in Orakzai entered its 18th day.
The UN announced on Friday that the deteriorating security situation in Orakzai and Kurram has forced 200,000 civilians to flee since November last year.