Can I request flight certificate for Travel insurance claims?

I am a passenger in flight number 3U 8719 on 12 Apr 2016 from Lhasa,China to Kathmandu,Nepal.
Accorrding to your flight was delay because bad weather in Kathmantu have an affect to my next two flights which one from Kathmandu,Nepal to New Delhi, and New Delhi, India to Leh, India. I missed 2 flights and bought the new tickets
Hence, I would like to require the flight certificate for travel insurance claims from your airlines. Refer to the requirement of the insurance company.
They require the two letters, which one from the aircraft authorithy who is response to these fight and one from your airlines for confirm that the flight was delay and give a reason of delay. For more information Please check your email : e-bookingservicescal.com.cn