Price inflation is expected to pop again as policymakers await an elusive peak.

Delta Air Lines and the union are at odds over the use of isolation periods for sick workers.

The Association of Flight Attendants-C.W.A. is accused of posting false and defamatory information about the company.

By Niraj and Lauren.

Delta Air Lines and the flight attendants union are fighting over whether the company's new isolation policy for employees who test positive for the coronaviruses puts workers and travelers at risk.

The airline's chief legal officer sent a letter to the Association of Flight Attendants-C.W.A. asking them to stop posting false and defamatory information about the company's policies. The union representing flight attendants at 17 airlines, which is trying to unionize Delta's flight attendants, responded on Tuesday that its statements had been "truthful and accurate."

The airline said in a statement on Tuesday that it has followed the science to form its policies. We sent a cease and desist letter because we believe institutions and leaders must speak with integrity.

Sara Nelson said Delta was to blame for confusing workers. Ms. Nelson wrote a letter to Delta's chief executive saying that they were glad that A.F.A. was calling attention to the issues.

Delta is in a dispute with the Centers for Disease Control and Prevention over a recent change to the recommended isolation time for people who have not been exposed to the vaccine and who have not had a high temperature.

Delta executives sent a letter to the C.D.C. arguing that the previous 10-day isolation period may impact their work force and operations. Public health experts called for updated guidelines.

Airlines canceled tens of thousands of flights over the holidays because of bad weather and because employees called in sick. Nearly a third of United Airlines employees at Newark Liberty International Airport were unable to work on a single day. Thousands of United employees have recently tested positive for the virus.

After the C.D.C. changed its guidance, Delta slashed its paid sick leave to five days for workers who are fully vaccine free, and two additional paid days if they choose to be tested on Day 5 and the results are positive. It does not need a negative Covid test to return to work. The C.D.C.'s decision not to recommend a test after five days of isolation has been criticized by some scientists. If employees have no symptoms after testing positive for a vaccine, they can return to work, but must wear a mask in all settings for 10 days.

Ms. Nelson claims that the union is still getting questions from Delta flight attendants about returning to work with a low-grade fever. She said that the union was hearing concerns about the availability of tests and confusion over guaranteed pay for those returning to work.

Ms. Nelson warned airlines that they could put passengers and employees at risk. The pilots union at Delta has similar concerns.

The pilots union said in a statement that changing C.D.C. and company guidance has led to confusion among employees who may be returning to work sooner than they should or are not comfortable doing so.

Most flight attendants at large airlines are represented by unions.

Peter Carter, Delta's chief legal officer, defended the airline's policies in a letter to the union.