In aviation:

• Pacific Island Aviation
  Pacific Island Aviation
  Pacific Island Aviation was an airline headquartered on the second floor of the Cabrera Center in Garapan, Saipan, Northern Mariana Islands. It operated passenger and cargo services. Its main base was Saipan International Airport...
  
  
• Pakistan International Airlines
  Pakistan International Airlines
  Pakistan International Airlines Corporation commonly known as PIA, is the flag carrier airline of Pakistan. The airline has its head office on the grounds of Jinnah International Airport in Karachi. and operates scheduled services to 24 domestic destinations and 38 international destinations in 27...
  
  , the flag carrier of Pakistan.
• Pearson International Airport, Toronto, Ontario (IATA: YYZ, ICAO: CYYZ)
• Peoria International Airport IATA code
• Peruvian International Airlines
  Peruvian International Airlines
  Peruvian International Airways was the first international airline from Peru and operated from 1947 to 1949.-Company history:The international air services provided to and from Peru from the mid forties until the beginning of the decade of the sixties was under dominance of the Panagra...
  
  , an international airline that operated from 1947 to 1949.

In science:

• Papers from the Institute of Archaeology
  Papers from the Institute of Archaeology
  Papers from the Institute of Archaeology, or PIA, is a peer-reviewed academic journal, published annually by the Institute of Archaeology at University College London...
  
  , an academic journal published by the Institute of Archaeology, University College London
• Pristane induced arthritis (a rheumatoid arthritis
  Rheumatoid arthritis
  Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...
  
   model in rats)
• Purified Isophthalic Acid
  Isophthalic acid
  Isophthalic acid is an organic compound with the formula C6H42. This colourless solid is an isomer of phthalic acid and terephthalic acid. These aromatic dicarboxylic acids are used as precursors to commercially important polymers, e.g. the fire-resistant material Nomex...
  
  , an aromatic dicarboxylic acid

In technology:

• Parallel interface adapter
  Parallel port
  A parallel port is a type of interface found on computers for connecting various peripherals. In computing, a parallel port is a parallel communication physical interface. It is also known as a printer port or Centronics port...
  
  
• Peripheral Interface Adapter
  Peripheral Interface Adapter
  The Peripheral Interface Adapter is a peripheral integrated circuit providing parallel I/O interfacing capability for microprocessor systems. Common PIAs include the Motorola MC6820 and MC6821, and the MOS Technology MCS6520, all of which are functionally identical but have slightly different...
  
  , an integrated circuit such as the Motorola MC6820
• Primary Interop Assembly, a type of .NET assembly
  .NET assembly
  In the .NET framework, an assembly is a compiled code library used for deployment, versioning, and security. There are two types: process assemblies and library assemblies . A process assembly represents a process that will use classes defined in library assemblies...
  
   dealing with interaction between managed code and COM objects
• Programmable Interconnect Array

Other uses include:

• Personal Information Agent
  Personal Information Agent
  A Personal Information Agent is an individual, business or organization who is expressly authorized by another identifiable individual in dealings with third persons, businesses or organizations concerning the Personally identifiable information , of that identifiable individual and the records...
  
  
• Philippine Information Agency
• Planned Incremental Availability, a U.S. Navy term involving a ship maintenance and overhaul cycle
• Post-Indictment Arraignment
  Arraignment
  Arraignment is a formal reading of a criminal complaint in the presence of the defendant to inform the defendant of the charges against him or her. In response to arraignment, the accused is expected to enter a plea...
  
  
• Primary Insurance Amount
  Primary Insurance Amount
  The Primary Insurance Amount , for the purposes of the Social Security Administration, is the amount which is used as the beginning point in calculating any benefit payable under Title II of the Social Security Act...
  
  , in regards to benefits payable under Title II of the Social Security Act
• Princeton-in-Asia
  Princeton-in-Asia
  Princeton in Asia is a nonprofit organization that helps recent college graduates obtain yearlong jobs with educational institutions, businesses, media organizations, and NGOs throughout Asia...
  
  , a nonprofit organization that helps recent college graduates obtain yearlong jobs with educational institutions, businesses, media organizations, and NGOs throughout Asia
• Printing Industries of America
  Printing Industries of America
  Printing Industries of America is a nonprofit trade association which advocates for the United States printing industry.It is the world’s largest graphic arts trade association, representing more than 10,000 member companies and an industry with more than $174.4 billion in revenue and 1 million...
  
  
• Privacy Impact Assessment
• Private Investigation Administrator, in Korea
• Proprietary Information Agreement
  Non-disclosure agreement
  A non-disclosure agreement , also known as a confidentiality agreement , confidential disclosure agreement , proprietary information agreement , or secrecy agreement, is a legal contract between at least two parties that outlines confidential material, knowledge, or information that the parties...
  
  , also known as Non-disclosure agreement