May calls Trump as Boeing argument forces Bombardier
In 2016, Canadian Company Bombardier won an order to transfer up to 125 CSeries passenger jets to US airline Delta.
The feathers for the CSeries developed at Bombardier's Belfast plant.
However, enemy plane company Boeing has criticized to the US system that the work was wrongly financed by the Canadian state.
The US Department of Commerce is because of making a rule later in this current month.
The CSeries project guides hundreds of services in Belfast.
A person said the system "is working tirelessly to guard Bombardier's works and its great skilled employees in Belfast".
"Ministers all over system have occupied quickly and widely with Boeing, Bombardier, the US and Canadian system," they said.
"Our main concern is to support Boeing to goes down its case and look for a meeting resolution with Bombardier."
The person said Mrs May increase the problem and her worry to secure services in Northern Ireland in a call with President Donald Trump previous week.
They also said Business Secretary Greg Clark went to Chicago to talk with Boeing's chairman. He is the president and chief executive officer of Dennis Muilenburg.
Bombardier managers in Belfast are also known to have recently detailed business units about the importance of the case.
Boeing has supposed that Bombardier occupied in "price removal" by accepting to sell 75 of their aircraft for almost $14 m (£10.6m) down their cost price.
The company said it had demanded to the International Trade Commission "to return a stage playing field in the US single walkaway airplane market".
"Boeing had to take act as financed market race has hurt us now and will carry to hurt us for the years to come, and we could not stay by given this clear state of illegal removal," it said in a word.
"Global business only works if all will play by the same policy of the road, and that's the main that finally develops the highest value for Canada, the United Kingdom, the United States, and our aerospace industry."
It also focused out that the Delta contract came after the regional government in Quebec effectively bailed out the CSeries event with a $1 bn investment.
"Fairness mixtures from government safer not only saved the event but have given Bombardier the source it requires to forcefully point to the US market," it said.
Bombardier has explained the claims as "strange" and said the system investments "comply with the laws and rules in the legally where we do trade".