If you are flying from below mentioned countries or airport, you need to carry a negative PCR certificate issued by a local government approved laboratory to be accepted on the flight. You must get your test certificate form the specific lab if the UAE government has specified a designated laboratory in your country of origin. This certificate must be issued no more than 96 hours before departure.
• Russian Federation
• USA – Dallas Fort Worth (DFW), Houston (IAH), Los Angeles (LAX), San Francisco (SFO), Fort Lauderdale (FLL) and Orlando (MCO), including passengers originating from California, Florida and Texas connecting to an Emirates flight from any of our airports worldwide to Dubai.
Source: Emirates Airline