[{"_id":{"$oid":"5bc7a1d14cedfd0006445b10"},"externalId":{"$numberLong":"70285"},"passengers":[{"_id":{"$numberLong":"3757"},"name":"abc","email":"abc@xyz.com"},{"_id":{"$numberLong":"398"},"name":"abc n","email":"abc@xyz.com"}]},{"_id":{"$oid":"5bc7a1d14cedfd0006445b11"},"externalId":{"$numberLong":"70286"},"passengers":[{"_id":{"$numberLong":"3758"},"name":"abc","email":"abc@xyz.com"},{"_id":{"$numberLong":"399"},"name":"abc n","email":"def@xyz.com"}]}]

db.collection.find({$expr:{$eq:[{$arrayElemAt:["$passengers.email",0]},{$arrayElemAt:["$passengers.email",1]}]}})