214 F.3d 795 (7th Cir. 2000)
Kenneth Sandstrom,    Plaintiff-Appellant,v.Cultor Food Science, Incorporated,    Defendant-Appellee.
No. 99-2331
In the  United States Court of Appeals  For the Seventh Circuit
Argued April 25, 2000
Decided May 25, 2000

Appeal from the United States District Court  for the Northern District of Illinois, Eastern  Division.  No. 97 C 8216--James F. Holderman, Judge.
Before Posner, Chief Judge, and Easterbrook  and Evans, Circuit Judges.
Easterbrook, Circuit Judge.


1
American  Xyrofin, a manufacturer of food  additives, was sold, merged, and  reorganized early in 1996, with  predictable consequences for some of its  executives. Cultor U.S. Inc. acquired  Xyrofin in January 1996 and renamed the  new subsidiary Cultor Food Science (cfs).  Soon Cultor Limited (the parent of Cultor  U.S.) bought another food additives group  from Pfizer, Inc., and merged this  business into cfs. As part of the  acquisition, Cultor promised Pfizer that  it would give Pfizer employees who joined  cfs but later lost their jobs benefits  tracking those of the severance-payment  plan that Pfizer maintained under the  Employee Retirement Income Security Act  (erisa). When in March 1996 cfs ended the  employment of Violeta Velasco, who came  from Xyrofin (which lacked a severance-  benefit plan), it offered her a severance  package: six weeks' pay, plus one  additional week's pay for each year she  had been employed by Xyrofin, both  doubled if she signed a release of any  legal claims against cfs. Toward the end  of March cfs decided that the services of  Kenneth Sandstrom, Velasco's supervisor,  also were no longer necessary. Sandstrom,  unlike Velasco, was not offered a  severance package. He filed this suit  under sec.502(a) (1)(B) of erisa, 29  U.S.C. sec.1132(a)(1)(B), contending that  the offer to Velasco demonstrated that cfs  had an "informal plan for severance  benefits" that applied to him too. The  district court disagreed and granted  summary judgment for cfs. 1999 U.S. Dist.  Lexis 6525 (N.D. Ill. Apr. 26, 1999).


2
Briefs filed in this court dwell on two  questions: whether Sandstrom has produced  evidence from which a reasonable trier of  fact could conclude that cfs "intended" to  establish an "informal" (which is to say,  unwritten) severance-benefit plan and, if  so, whether the terms of that plan are  sufficiently definite to support a  remedy. They debate, for example, whether  Barton Finegan, the vice president of  human resources who approved the offer to  Velasco, had authority to establish a  plan on behalf of cfs. They also explore  whether the Velasco offer sets out the  terms of the plan or whether, instead,  these terms may be found elsewhere--  perhaps in a check sent to Velasco (which  gave her one week's pay in addition to  what the offer promised) or perhaps in  the (written) plan for employees cfs  inherited from Pfizer. This plan had a  13-week base plus triple the week's-pay-  per-prior-year if the employee signed a  release. Nor can the parties agree on  whether the "informal plan" afforded  benefits in lieu of notice (so that an  employee who remained on the payroll  after notice of termination would have  severance benefits reduced by the number  of weeks of employment yet to go) or was  on top of whatever wages the employee  earned. If cfs created a plan by making an  offer to Velasco, did it amend or abolish  the plan by not making a similar offer to  Sandstrom? These are enigmas, which  exemplify a deeper problem that the  parties have not mentioned: does erisa  contemplate unwritten plans? None of  these uncertainties would exist if the  plan were on paper.


3
Several of our cases say that it is  possible to have an unwritten pension or  welfare-benefit plan under erisa, if the  plan is "a 'reality,' which requires . .  . that the court be able to determine  'whether from the surrounding  circumstances a reasonable person could  ascertain the intended benefits,  beneficiaries, source of financing, and  procedures for receiving benefits.'"  James v. National Business Systems, Inc.,  924 F.2d 718, 720 (7th Cir. 1991),  quoting from Donovan v. Dillingham, 688  F.2d 1367, 1373 (11th Cir. 1982) (en  banc). See also Diak v. Dwyer, Costello &  Knox, P.C., 33 F.3d 809, 811-12 (7th Cir.  1994); Ed Miniat, Inc. v. Globe Life  Insurance Group, Inc., 805 F.2d 732, 738-  39 (7th Cir. 1986). It is not clear that  the approach taken in Dillingham is  compatible with more recent decisions of  the Supreme Court, which emphasize  different considerations when asking  whether an informal policy or arrangement  is a "plan." See Massachusetts v. Morash,  490 U.S. 107 (1989); Fort Halifax Packing  Co. v. Coyne, 482 U.S. 1 (1987). Both  Morash and Ft. Halifax evince reluctance  to find that regular and predictable  awards of severance or vacation payments  establish a "plan," given the frequency  with which these benefits are the subject  of bilateral negotiations between  employers and departing employees. But we  need not pursue this subject, because cfs  had an express plan, which did not cover  Sandstrom.


4
Written plans may be altered only in  writing. Statements by plan  administrators, side agreements and  understandings, or even special offers  made to many of a firm's employees, do  not change the contents of the plan  applicable to other employees. See, e.g.,  Central States Pension Fund v. Gerber  Truck Service, Inc., 870 F.2d 1148 (7th  Cir. 1989) (en banc); Frahm v. Equitable  Life Assurance Society, 137 F.3d 955, 960  (7th Cir. 1998); Central States Pension  Fund v. Joe McClelland, Inc., 23 F.3d  1256 (7th Cir. 1994). Likewise,  statements or conduct by bureaucrats  implementing a plan do not estop the  employer to enforce the plan's written  terms, and although we have not barred  the door we have made it clear that only  extreme circumstances (not yet seen)  justify estoppel. See, e.g., Shields v.  Teamsters Pension Plan, 188 F.3d 895 (7th  Cir. 1999); Plumb v. Fluid Pump Service,  Inc., 124 F.3d 849, 856 (7th Cir. 1997);  Schoonmaker v. Employee Savings Plan of  Amoco Corp., 987 F.2d 410 (7th Cir.  1993).


5
These decisions are fatal to Sandstrom's  position, for his claim must be that cfs  amended its formal plan (the one  applicable only to former Pfizer  employees) by making the offer to  Velasco. Yet that is not the means erisa  contemplates for plan amendments. See  Curtiss-Wright Corp. v. Schoonejongen,  514 U.S. 73 (1995). Sandstrom evidently  believes that erisa forbids bilateral  deals between an employer and individual  employees, so that the offer to Velasco  must be a manifestation of a generally  applicable "plan." Our opinion in Frahm  rejects that position, holding that  bilateral arrangements are compatible  with erisa and do not modify the plan  applicable to other employees who did not receive the offers or estop the employer  to enforce the plan's written terms. 137  F.3d at 957-58. See also McNab v. General  Motors Corp., 162 F.3d 959 (7th Cir.  1998). Accord, Sprague v. General Motors  Corp., 133 F.3d 388, 403 (6th Cir. 1998)  (en banc). Sandstrom was not entitled to  severance benefits under the terms of the  Pfizer acquisition, so the judgment of  the district court is    affirmed.

